Research ArticleResearch on Pressure Drop in the Accelerate Zone of HorizontalConveying of Concrete Spraying

Guanguo Ma1 Zhaoxia Liu 1 Xiaobing Gong1 Lianjun Chen 1 Guoming Liu2

Gang Pan 1 and Qizheng Dong1

1College of Mining and Safety Engineering Shandong University of Science and Technology Qingdao 266590 China2Chongqing Research Institute of China Coal Science and Industry Group Chongqing 400016 China

Correspondence should be addressed to Zhaoxia Liu zhaoxialiu163com and Lianjun Chen skyskjxz163com

Received 28 April 2019 Revised 17 July 2019 Accepted 25 July 2019 Published 23 December 2019

Academic Editor Xu Yang

Copyright copy 2019 Guanguo Ma et al 1is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

A pressure transmitter was installed at a specific position in a concrete conveying line to disclose the pressure drop whencompressed air was conveyed during concrete spraying A statistical analysis of the pressure at different positions was undertakenExperimental results demonstrated that in the accelerate zone of horizontal conveying of concrete in the line the pressure dropmainly occurred during the acceleration collision and friction processes 1e momentum equation was introduced during theexperiment which interpreted the pressure drop caused by the accelerated conveying of concrete 1e theoretical equation wascorrected based on the results of theoretical experiments by introducing the value of α and the experimental results were thenoptimized thus obtaining an approximate model of pressure drop during the conveying of concrete In addition experimentalresults were compared with a model equation that showed the reliability of the proposed model Research conclusions are of greatsignificance to regulate the pressure drop in the conveying line of concretes to design working parameters of concrete sprayingdevices and to predict the ultimate distance for the conveying of concrete

1 Introduction

Concrete spraying technology is extensively applied inunderground projects (eg railway and tunnel) and tunnelconstruction in coal mines in China [1ndash3] Because of itsassociated conveniences wind-driven concrete sprayingtechnology has been widely applied Concrete spraying is aprocess that conveys stirred concrete in a closed line bycompressed air to the nozzle and is then sprayed which isthe process of pneumatic conveying However the con-veying process of concrete is relatively complicated and itlacks theoretical references related to the prediction ofconcrete conveying distance Instead generally the concreteconveying distance can only be estimated 1erefore it isnecessary to study the process and mechanism of wind-driven concrete conveying Research results provide theo-retical references for the design of a shotcrete machine andprediction of the conveying distance

Pressure drop should be considered in the design of aconcrete conveying system When calculating the pressuredrop in delivery lines the classic phase diagram is oftenapplied in which the pressure drop in unit length of theline is expressed as a function related to speed [4 5]Forces in concrete and on the pipe walls predict thepressure drop in the conveying of concrete Naveh et alshowed the effect of the slip velocity of particles onpressure drop by studying the pressure drop during thepneumatic transmission of various types of particles1ese authors believed that understanding the velocity ofparticles in the steady-state region was vital for reliablydesigning the entire conveying process [6] Brown showedthat the flow of particles and fluid were the primary causesof pressure drop during pneumatic transmission andconstructed a linear equation to express pressure dropduring the velocity stabilization zone [7] and it can bedescribed as

HindawiAdvances in Civil EngineeringVolume 2019 Article ID 7953434 10 pageshttpsdoiorg10115520197953434

ΔPss ΔPc + ΔPf (1)

where ΔPss is the constant pressure drop ΔPc is the pressuredrop caused by concrete and ΔPf is the pressure dropcaused by compressed air

Here

ΔPf fDρfu2

f2D

L (2)

where fD is the coefficient of friction in pipe ρf is the densityof compressed air uf is the air velocity D is the internaldiameter of the pipeline and L is the conveying distance

Conveying concrete using the driving effect of compressedair exists in a suspension flow state Because of the high fluidvelocity the influences of gravity on the state of conveying canbe neglected [8ndash10] At the start of conveying concrete isconveyed into the line by a shotcrete machine at zero velocityunder the action of compressed air Momentum is transferredfrom air to concrete and can trigger disturbance of air flow aswell as changes in momentum Air pressure is needed duringthis process and is significantly higher than that requiredduring single-phase flow [11ndash13] 1erefore the acceleratedconveying of concrete in line requires an accelerate zone thatrefers to the process from the beginning of the acceleratedconveying of concrete to the stable conveying speed [14]

In the present study the pressure drop caused byaccelerated conveying of concrete is considered During theconveying of concrete the pressure drop in the acceleratezone is mainly attributed to acceleration collision andfriction of concrete 1e acceleration of concrete only occursin the accelerate zone whereas collision and friction occurthroughout the conveying of concrete1e total pressure dropin the accelerate zone can be defined as the sum of the steady-state pressure drop and accelerated pressure drop [8] 1epressure drop caused by acceleration must be first consideredwhen analyzing the pressure drop in the horizontal acceleratezone of concrete transfer 1e pressure drop caused by ac-celeration is generally determined by pressure distribution inthe accelerate zone 1e accelerate zone from the shotcretemachine to the nozzle is mainly distributed under two sit-uations the first accelerate zone is called the initial acceleratezone when concrete and compressed air begin to flow 1esecond accelerate zone is the region after the concrete passesthrough the bent pipe Studying the law of pressure drop inthe accelerate zone of concrete has great significance forpredicting the conveying distance of concrete [15 16]

Many researchers have proven that the pressure dropcaused by concrete friction and collision in the steady-stateregion was different from that in the accelerate zone Hencethe pressure drop in the accelerate zone cannot be predictedby the momentum equation of concrete and is often pre-dicted by the correlation between concrete collision andfriction during the conveying process [17ndash20]

Ottjes has researched the movement of the particle inhorizontal pipes which took the lifting force of materialsand the inelastic collision between particles and pipe wallinto account [21] Nguyen analyzed the movement of singleparticles in horizontal pipelines especially considering theeffect of Magnus [22] Huber and Sommerfeld conducted a

three-dimensional numerical simulation of the dilute phaseflow pneumatic transport and predicted the particle dis-tribution in horizontal pipelines and 90-degree bent pipes byconsidering two-way coupling turbulence and the disper-sion law of turbulent particles [23]

Hanley et al proposed a method based on processrandomness to quantify particle collision in the line that canbe used to express the pressure drop caused by the collisionof internal aggregates during the acceleration process [24]Klinzing and Basha studied variations in average particlespeed based on abundant experimental data and constructeda correlation providing reasonable theoretical references forthe conveying of concrete under the effect of compressed air[25] Merkus and Meesters proposed a method to describethe pressure drop during the acceleration process using themomentum equation 1ey expressed the variation equationof concrete particles and air momentum and proposed amethod to predict the pressure drop in accelerationHowever they did not construct an appropriate pressuredrop model in the accelerate zone thus failing to judge theaccuracy of the pressure drop curve in the accelerate zone[26]

1e present study focused on studying the law ofpressure drop in the accelerate zone of the pneumatictransmission of concrete 1is was to study the relationshipbetween the variation law of the momentum of air andconcrete particles and the pressure drop in the acceleratezone1e air-concrete ratio was changed by altering the flowrate of compressed air and the supply quantity of concreteIn addition the input pressure of compressed air waschanged Pressure changes in the line were measured by apressure transmitter A mathematical model was con-structed to analyze the law of pressure drop in the acceleratezone of pneumatic transmission of concrete Researchconclusions have great significance for predicting the dis-tance of concrete and matching the optimal air supplypressure

2 Experimental Conditions

21 Experimental Apparatus Two specifications (20-inchand 25-inch diameter) of concrete conveying lines wereset in the pressure drop experiment in the accelerate zone1e feeder used the PTS7 pushing chained shotcretemachine made by Shandong Wit Laboratory MiningEquipment Co Ltd (Figure 1) 1e shotcrete machineconveys concrete to the outlet using a piston and achievesthe long-distance conveying of concrete via compressedair 1is equipment is applicable to dry and wet concretespraying 1e maximum spraying capability of thisshotcrete machine was 6m3h Its theoretical gas con-sumption and rated wind pressure were 8m3min and05MPa respectively 1e shotcrete machine motor usedthe variable-frequency control of speed 1e rotatingspeed of the motor could be adjusted by the transducerthus controlling concrete throughput during concreteconveying

1e structure of the concrete line is shown in Figure 2which covers four bent lines 1e radius of two of the bent

2 Advances in Civil Engineering

lines was 1m and the radius of the other two bent lines was06m To assure consistency of the concrete lines the bend ofthe line was fixed onto the self-made bend fixing device usingan ordinary rubber hose During line pavement horizon-tality and coaxial performance of concrete lines were verifiedby the rotating laser

22 Experimental Instruments Compressed air enters theshotcrete machine via the regulating valve and vortexshedding flowmeter to adjust and measure the input pres-sure and flow rate of compressed air In the present ex-periment the pressure drop in the concrete lines wasmeasured by a high-accuracy flat film pressure transmitter1e sensor applied the Dwyer FDT series of the flat filmpressure transmitter made by the Deville Company (USA)with a measuring range of 0ndash16MPa and an accuracy of002 According to the service manual of the sensor thepressure transmitter was installed on a section of the

specially made line and the concrete line was fixed onto arubber hose by a special pipe clamp To prevent scratches ofthe sensor by gravels a strainer was installed before thepressure transmitter (Figure 3)

1e temperature and flow rate of the compressed airwere measured by a vortex shedding flowmeter 1e tem-perature was viewed as constant throughout the conveyingof concrete Hence the temperature in the entire line wasequal to the inlet temperature 1e temperature of the mixedconcrete in all experiments was controlled between 15 and20degC

1e rotating speed of the chain wheel was 20 rminwhen the shotcrete machine reached the maximum de-livery capacity (6m3h) 1e feeding speed of the shotcretemachine could be adjusted by a transducer 1e vortexshedding flowmeter for measuring the flow rate ofcompressed air and the pressure transmitter for mea-suring pressure in the lines were read and data werereceived by the paperless recorder

Vortex street flowmeterPressure gauge

Blast pipe

Outlet

Shotcrete machine

Concrete linePressure transmitter

Figure 1 Structure of the PTS7 pushing chained shotcrete machine

Flow

R = 1m

R = 06m

R = 1mR = 06m

P-AP-B

P-CP-D

P-EP-1

P-2P-3

P-4P-5

P-6P-7

P-8P-9

Pmdash1Pressure transducer numberNotation for pressure transducer

2m typical dist

Figure 2 Structure of concrete lines

Advances in Civil Engineering 3

23 Experimental Materials

231 Cement 1e cement used in the experiments wasPO425 cement made by the Shandong Shanshui CementGroup Its purity and specific gravity were 3100 cm2g and314 respectively

232 Aggregates Aggregates can be divided into fine andcoarse aggregates 1e former used natural river sands Afterscreening its fineness modulus silt content and apparentdensity were 275 12 and 268 gcm3 respectively 1ecoarse aggregate applied was ordinary limestone fragmentswhose maximum grain size was less than 10mm Contin-uous grading was performed to remove impurities beforemixing the fine and coarse aggregates 1e grading curves offine and coarse aggregates are shown in Figure 4 and theyconform to limitations of recommended grades in the na-tional standard GB50086-2001 [27]

233 Chemical Admixture 1e main chemical admixturein this experiment was accelerator 1is accelerator was akind of powdery solid with density 4 gcm3

234 Concrete Ratio In the experiment the concrete wasmade up according to the common concrete ratio in the coalmine Also the concrete ratio was cement fine aggregates coarse aggregates accelerator 1 2 2 003

3 Experimental and Analysis Methods

1e PTS7 pushing chained shotcrete machine used in theexperiments can achieve material feeding at a constant speedby motor-driven piston motion 1e prediction of thepressure drop during wind-driven conveying of concretepredicts the pressure drop in unit length In concrete linesthe acceleration process of concrete mainly distributes at the

initial conveying section and after passing the bent line 1eeffects of these acceleration processes are identical 1ere-fore attention was given to the pressure drop during theacceleration processes of concrete in the initial section andafter passing the bent line in the experiments

In the pressure drop test during concrete conveying thepressure in the concrete lines must be measured To preventscratches on the pressure transmitter from the gravels theexperiment was performed using the following method

Before the commencement of the experiment theconcrete lines were verified by only supplying compressedair

(1) Figure 3(a) shows that without the strainer thebottom of the pressure transmitter was installed ontothe inner wall of the concrete lines 1e compressedair was supplied and the pressure at different po-sitions along the line was recorded by pressuretransmitters 1is is the universal method for thepressure transmitter and it can accurately measurethe pressure in concrete lines

Transducer rider

Pressure transducer

Adjusting nut

(a)

Transducer rider

Pressure transducer

Adjusting nut Strainer

(b)

Figure 3 Installation structure of the pressure transmitter on lines (a) Standard installation structure of the pressure transmitter (b)Installation structure of the pressure transmitter with strainer

Fine agg limitsCoarse agg limitsGravel gradation

Perc

enta

ge p

asse

d by

wei

ght (

)

Sand gradation

0

40

20

60

80

100

10 10010Sieve size (mm)

Figure 4 Grade curves of fine and coarse aggregates

4 Advances in Civil Engineering

(2) In Figure 3(b) a strainer was placed on the mountingbase of the pressure transmitter Later the pressuretransmitter was installed to keep the bottom of thepressure transmitter 2mm away from the strainerCompressed air was supplied and pressures along theconcrete line were recorded by the pressure transmitter

Pressures under the above two conditions aresummarized in Figure 5 During this process thepressures at the different positions that were measuredby the two methods had a fixed difference of ΔP0 Whenthe pressure in the concrete conveying was measured bythe method in Figure 3(b) the pressure in the concreteline was equal to the sum of the measured pressure P0and ΔP0 In other words pressure changes after theaddition of a strainer could be used to reflect thepressure changes in the concrete lines throughoutconveying

1e acceleration pressure drop in the horizontal sectionof the concrete conveying was mainly caused by the meanpressure difference measured by the pressure transmitter1e measured acceleration pressure drop between any twopoints in the analysis region was discussed Howeverwhether concrete was in the initial section or had passed thebent line was neglected thus it was believed that the mo-mentum and energy changes were the same given the samevelocity changes

During the experiment pressure drop in the acceleratezone occurred as shown in Figure 6 1e pressure dropcurve shows that the pressure drop in the accelerate zonereached a relatively stable trend 1e pressure curveduring this process was fitted and a straight line repre-senting the steady-state pressure drop was deduced basedon the final process of the stable pressure drop Based onthis deduced straight line the pressure at zero speed couldbe determined

In Figure 6 ΔPacctotal is the total pressure drop in theaccelerate zone and ΔPacc is the acceleration pressure dropof concrete

According to reverse deduction from the stable value ofthe above curves energy loss under steady state can beobtained from the index trend and linear pressure gradienttrend of floating points leading to the acceleration ofpressure drop and thus obtaining the actual pressure droptrend An exponential linear equation was fitted by thepressure fitting curve in Figure 6

P0 p1 middot eminus xp2 + p3 middot x + p4 (3)

Here x is the length of the test section and p1 p2 p3 andp4 are constants 1e numerical value in Figure 6 wasbrought into equation (3) thus obtaining the followingequation

P0 11 middot eminus 036x

minus 45x + 307 (4)

1is pressure-distance relation equation covers twoparts (1) p1 middot eminus xp2 is the exponential function that reflectsthe pressure drop caused by the acceleration in the concreteline (2) p3 middot x + p4 is the linear function that reflects the

pressure drop caused by concrete collision and friction in theline Under this circumstance the pressure drop is dis-tributed uniformly Based on the above curves we can obtainthe following results

(a) Steady pressure drop in the concrete line(b) Accelerated pressure drop in the concrete line(c) 1e pressure at the beginning of acceleration is

difficult to measure Under this circumstance thepressure at the beginning of acceleration can bededuced by the equation 1us the pressure dropfrom zero to a steady speed could be calculated

(d) Length of the accelerate zone (part 1 in the equationis approaching zero)

To predict the length of the accelerate zone duringconcrete conveying Wei et al introduced the Archimedesnumber [28] 1e Archimedes number mainly reflects theratio between buoyancy and viscosity force and can beexpressed as

∆P

With strainerWithout strainer

260

270

280

290

300

310

320

330

340

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

Figure 5 Effects of the strainer in the pressure transmitter on thegas-phase pressure drop

Steady-statepressure drop

trendPressure point

Actual pressuredrop trend

Accelerate zone

Accelerate length

Steady-statezone

∆Pacc

∆Pacc total

∆Pss

260

270

280

290

300

310

320Pr

essu

re (k

Pa)

12106 8 14 162 4 18 200Distance (m)

Figure 6 Trend of pressure drop during concrete conveying

Advances in Civil Engineering 5

Ar ρc minus ρf( 1113857g middot d3

v2 middot ρf (5)

where Ar is the Archimedes number ρc is the density ofconcrete ρf is the density of air v is the kinematic viscosityand d is the mean diameter of concrete particles

In the present study the conveying speed of theconcrete particles was measured with a high-speedcamera Pressure changes in the concrete line weremeasured by the pressure transmitter 1e length of theaccelerate zone of concrete was expressed by particlespeed and pressure changes Moreover the relation be-tween the Archimedes number and length of the accel-erate zone was expressed as

Lacc 16Ar01 (6)

During the present experiment the total pressure dropin the accelerate zone was expressed as the sum of steady-state pressure drop and accelerated pressure drop (equation(7))1e accelerated pressure drop (ΔPacc) is the momentumequation of concrete and can be expressed as equation (8)

ΔPacctotal ΔPss + ΔPacc (7)

ΔPacc ΔPmom _msΔuc

A

_ms ucss minus 0( 1113857

A (8)

where ΔPacctotal is the total pressure drop of the acceleratezone ΔPacc is the accelerated pressure drop of concrete ΔPssis the constant pressure drop of concrete and _ms is the massvelocity of concrete particle flow

1e total pressure drop in equation (7)was used to calculatethe derivation of displacement and can be expressed as

dPacctotal

dxdPss

dx+dPacc

dx (9)

To analyze the steady-state speed and transient speedduring concrete conveying an equation was constructed inthe present experiment with reference to the study by Weiet al [28]

ucss

uf 1 minus 0072 Ar middot

ρc minus ρfv2 middot ρf

1113890 1113891

0091

(10)

uc

ucss 1 minus e

minus 48xLacc (11)

where ucss is the steady speed of concrete uc is the initialvelocity of concrete and uf is the air velocity 1e derivativeof distance was calculated based on equation (10) and wasbrought into equation (11)

dPacctotal

dxdPss

dx+

_ms

A

duc

dx (12)

1e value of uc in equation (8) was brought into equation(12) to obtain

dPacctotal

dxdPss

dx+

_ms middot ucss

A

duc

dx1 minus e

minus 48xLacc1113872 1113873 (13)

Based on the integration of the displacement x throughequation (13) the following was obtained

1113946Lacc

0

dPacctotal

dx1113888 1113889dx 1113946

Lacc

0

dPss

dx1113888 1113889dx minus 1113946

Lacc

0

_ms middot ucss

A

48Lacc

1 minus eminus 48xLacc1113872 1113873dx

(14)

1erefore

Ptotal _ms

Aucss middot e

minus 48Lacc( )x+ p3 middot x + p4 (15)

By comparing equations (3) and (15) the following wasobtained

p1 _ms

Aucss

p2 minus48Lacc

x

(16)

1us the accelerated pressure drop of concrete can beexpressed as

ΔPacc _ms

Aucss middot e

minus 48Lacc( )x

_ms

Aucss middot e

minus 4816Ar01( )x

_ms

Aucss

middot eminus 4816 ρcminus ρf( )gmiddotd3( ) v2 middotρf( )( )

01( 1113857x

(17)

To protect the accuracy of the conclusions the concreteflow trend in the constant speed section was verified bychanging the supply quantity of concrete and air input 1estarting point of the constant speed section was set at 15mafter the bent line In the experiment the concrete supplywas controlled by the rotating speed of the motor of thetransducer During this process the relationship between thepressure drop during concrete conveying and concretesupply was found as shown in Figure 71e figure shows theeffects of air flow and concrete supply quantity on pressuredrop during the conveying of concrete

However equation (7) focused on testing the physicalproperty of the accelerated pressure drop which is the re-lationship between the momentum equation and pneumatictransmission during the conveying of concrete To accuratelypredict the relationship of accelerated pressure drop in theconveying of concrete the correction factor αwas introduced toincrease the prediction accuracy 1erefore the prediction ofthe total pressure drop in the acceleration zonewas calculated as

ΔPacctotal αΔPss + ΔPacc (18)

4 Results and Discussions

It is very simple to predict the pressure drop during concreteconveying by experiments First it must be determined thatthe pressure drop during concrete conveying is caused byaccelerated conveying friction and the collision of con-cretes 1e pressure drop caused by the acceleration of

6 Advances in Civil Engineering

concrete is also called the accelerated pressure drop and itonly exists in the accelerate zone 1e pressure dropcaused by friction and collision is called the uniformpressure drop and it exists throughout the conveying ofconcrete 1erefore the pressure drop caused by accel-eration can be calculated by the accelerated pressure dropminus the uniform pressure In the calculation of pressuredrop during concrete conveying the sum of steady-statepressure drop and accelerated pressure drop is the totalpressure drop in the accelerate zone 1is relationship isbased on the hypothesis that the steady-state pressuredrop in the accelerate zone and constant speed section arethe same

When predicting the pressure drop during concreteconveying the accelerated pressure drop can be predictedby equation (8) Hence the steady-state speed in theconveying of concrete must be known which can be cal-culated by equations (10) and (11) During the presentexperiment the rotating speed of the motor was changed bythe transducer thus changing the mass flow rate duringconcrete conveying Simultaneously the pressures at dif-ferent positions in the accelerate zone and constant speedzone could be measured

1e experimental pressure drop trend of concrete underdifferent mass flow rates is shown in Figure 8 which iscomparing the curves drawn based on equation (17) Fig-ure 8 shows that the increasing trend of the curves underdifferent supply quantities of concrete is the same Based onthe comparison of the curves drawn in accordance withFigure 8 the theoretical trend might overlap with the actualcurve measured in the experiment If these two curvesoverlap then the actual pressure drop during concreteconveying is similar to the predicted pressure drop provingthe accuracy of the prediction If the actual pressure dropdoes not overlap with the predicted pressure drop thesteady-state pressure drop in the accelerate zone is differentfrom that in the constant speed zone

1e effects of concrete pressure (p0) at the beginningposition on the pressure drop trend along the concreteconveying are shown in Figure 9 Normalization of pressureduring concrete conveying based on p0 can decrease theinfluence of the air flow rate on the pressure measurementand the maximum error can be controlled within 2

During multiple experimental processes the value of αwas calculated by changing the air flow rate and feeding rateof concrete under different motor speeds

Accelerated pressure drop and uniform pressure dropduring the concrete conveying were predicted based on thevalue of α If α 1 the pressure drop caused by concretecollision and friction was the same in the constant speedsection If αlt 1 the pressure drop was relatively small be-cause of the low conveying speed of concrete In contrastαgt 1 indicates a high pressure drop because of the highconveying speed of concrete In the constant speed section ofconcrete particle collision was weak However particlecollision frequency was high and particle collision wasstrong in the accelerate zone resulting in the high energyloss of concrete particles 1erefore the pressure drop in theaccelerate zone was higher than that in the constant speedsection

1e difference between the experimental and theoreticalresults of concrete conveying was positively related to theconcrete throughput given the same flow rate of compressedair When the concrete throughput was small the experi-mental results and theoretical results were similar indicatingthat α was closer to 1 (Figure 10) With an increase ofconcrete throughput the difference of experimental andtheoretical results gradually increased 1e difference is thekey factor influencing the prediction of concrete conveying

Next the value of the transducer was fixed and theconcrete was input by the shotcrete machine at a constantfeeding rate Subsequently pressures at different points weretested by controlling the input of compressed air with the

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h

6m3h

Figure 8 Variation trend of concrete pressure

Stea

dy-s

tate

pre

ssur

e dro

p pe

run

it le

ngth

(Pa

m)

Concrete throughput4m3h5m3h6m3h

0

500

1000

1500

2000

2500

3000

38 42 46 50 54 58 62 66 7034Air flow rate (m3min)

Figure 7 Variations of pressure drop in the constant speed sectionwith air flow

Advances in Civil Engineering 7

regulating valve 1ere was a large difference between theexperimental results and theoretical results With an in-crease of air flow rate such differences decreased gradually1is difference was also a key factor that influenced theprediction of concrete conveying

Figures 10 and 11 show that the value of α had a directrelationship with concrete throughput and input of com-pressed air Tripathi et al tested materials of different grainsizes [29] and α can be defined as

α a + b middot eminus cmiddotμ

( 1113857 (19)

where μ mcmf is the ratio of concrete mass and air massExperimental data from Figures 11 and 12 were brought

into equation (19) yielding the following

α 12 + 011eminus 09μ

1113872 1113873 (20)

During the accelerated pressure drop experiment theconveying of concrete particles was accelerated at a specificspeed from one point and finally reached the movementtrend at a constant speed [30ndash32] 1e momentum equationwas used to calculate the pressure drop during this process

ΔPacc ΔPmom _ms middot Δuc

A

_ms middot ucss minus uc( 1113857

A (21)

Pressure drop is at equilibrium in the constant speedsection 1erefore the total accelerated pressure drop can begained from equations (18) (19) and (21) 1e totalaccelerated pressure drop was expressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961ΔPss +_ms middot ucss minus uc( 1113857

A

(22)

Also equations (1) and (2) were brought into equation(22) and thus the total accelerated pressure drop wasexpressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961 fDρfu2

f2D

L + ΔPc1113888 1113889

+_ms middot ucss minus uc( 1113857

A

(23)

To verify the accuracy of equation (20) the feedingrate of concrete was kept constant in the experiment 1econcrete-air ratio was changed by altering the air flow rateto analyze the pressure at different positions along theline Comparison between theoretical and experimental

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

65m3h

Figure 10 Comparison of theoretical and experimental pressuresafter adding α

Air flow

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

7m3min65m3min6m3min

55m3min

Figure 11 Comparison of pressure drop in the accelerate zone

ndash22

Air flowTheoretical trendExperimental trendError range

04

05

06

07

08

09

10

PP 0

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

Figure 9 Normalization trend under different wind speeds

8 Advances in Civil Engineering

pressures is shown in Figure 12 1e curve equationgained from the theoretical formula was similar to theexperimental results showing a maximum error of lessthan 10 1is verified the universality of equation (20)In this experiment pipe diameters of 20 inches and 25inches of the concrete line were applied Pressures atdifferent positions of the concrete line were tested by apressure transmitter (Figure 12) 1e maximum error wasless than 5 verifying the feasibility of equation (20)

5 Conclusions

In order to obtain the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying the concreteconveying pipeline was arranged to conduct the relatedconcrete conveying experiment 1e concrete was made upaccording to the common concrete ratio in the coal mineEach point pressure on the pipeline during the progress ofconveying was tested by the pressure transmitter set up onthe pipeline Also the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying was analyzed withmeasured pressure

1e results show that the pipeline pressure droppedrapidly at the beginning of the conveying and at the end ofthe bending pipe and the trend of the dropping linearly wasshowed gradually 1e accelerated pressure drop was ana-lyzed by combining experimental and momentum equationsduring concrete conveying 1e accelerated pressure dropwas analyzed which was mainly caused by accelerationfriction and the collision of concretes Also the friction andthe collision of concretes also exist in the zone of stableconvey

1e pressure drop curve was drawn according to thepressure at each point in the concrete conveying processAlso the mathematical model of pressure drop in theconcrete conveying process was set up To prevent random

interference factor from the friction and the collision andimproving the calculation accuracy the correction factor αwas introduced

Finally the measured pressures under different concretethroughputs and flow rates of compressed air were com-pared with the results from the mathematical model whichverified the accuracy of the mathematical model Also themain factors of pressure drop in the accelerate zone wereobtained as the ratio of the concrete mass and the com-pressed mass the initial velocity of the concrete the optimalfinal required velocity the feed speed of concrete and crosssection area of the conveying pipeline

Data Availability

1e data used to support the findings of this study areavailable from the corresponding author upon request

Additional Points

Innovations and highlights (1) Damage to the pressuretransmitter by concrete can be prevented by installing astrainer before the pressure transmitter (2) Variation laws ofpressure before and after the installation of a pressuretransmitter were studied by supplying air only (3) A sta-tistical analysis of the pressures at different positions alongthe concrete conveying line under different input quantitiesof concrete and compressed air was performed Based onthis the law of pressure drop during the conveying ofconcrete was discussed (4) 1e pressure drop in the lineduring the conveying of concrete was predicted

Conflicts of Interest

1e authors declare that they have no conflicts of interest

References

[1] L Chen G LiuW Cheng and G Pan ldquoPipe flow of pumpingwet shotcrete based on lubrication layerrdquo SpringerPlus vol 5no 1 p 945 2016

[2] Y Cai Y Jiang I Djamaluddin T Iura and T Esaki ldquoAnanalytical model considering interaction behavior of groutedrock bolts for convergence-confinement method in tunnelingdesignrdquo International Journal of Rock Mechanics and MiningSciences vol 76 pp 112ndash126 2015

[3] L Chen P Li G Liu W Cheng and Z Liu ldquoDevelopment ofcement dust suppression technology during shotcrete in mineof China-a reviewrdquo Journal of Loss Prevention in the ProcessIndustries vol 55 pp 232ndash242 2018

[4] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[5] Q Liu W Nie Y Hua H Peng and Z Liu ldquo1e effects of theinstallation position of a multi-radial swirling air-curtaingenerator on dust diffusion and pollution rules in a fully-mechanized excavation face a case studyrdquo Powder Technol-ogy vol 329 pp 371ndash385 2018

[6] R Naveh N M Tripathi and H Kalman ldquoExperimentalpressure drop analysis for horizontal dilute phase particle-fluid flowsrdquo Powder Technology vol 321 pp 353ndash368 2017

Pipe diameter

3

2inch25inch

Theoretical trendExperimental trend

5

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

Figure 12 Pressure drop at different specifications of concretelines

Advances in Civil Engineering 9

[7] O G Brown ldquo1e history of the Darcy-Weisbach equationfor pipe flow resistancerdquo in Proceedings of the Environmentaland Water Resources History pp 34ndash43 Washington DCUSA November 2003

[8] O Molerus ldquoOverview pneumatic transport of solidsrdquoPowder Technology vol 88 no 3 pp 309ndash321 1996

[9] Q LiuW Nie Y Hua H Peng C Liu and CWei ldquoResearchon tunnel ventilation systems dust diffusion and pollutionbehaviour by air curtains based on CFD technology and fieldmeasurementrdquo Building and Environment vol 147pp 444ndash460 2019

[10] Y-Q Zhang J-L Zhu X-H Wang X-W ZhangS-X Zhou and P Liang ldquoSimulation of large coal particlespyrolysis by circulating ash heat carrier toward the axialdimension of the moving bedrdquo Fuel Processing Technologyvol 154 pp 227ndash234 2016

[11] Y Tomita H Tashiro K Deguchi and T Jotaki ldquoSuddenexpansion of gas-solid two-phase flow in a piperdquo Physics ofFluids vol 23 no 4 pp 663ndash666 1980

[12] P Li Z Zhou L Chen G Liu and W Xiao ldquoResearch ondust suppression technology of shotcrete based on new sprayequipment and process optimizationrdquo Advances in CivilEngineering vol 2019 Article ID 4831215 11 pages 2019

[13] B Kong E Wang and Z Li ldquo1e effect of high temperatureenvironment on rock propertiesmdashan example of electro-magnetic radiation characterizationrdquo Environmental Scienceand Pollution Research vol 25 no 29 pp 1ndash11 2018

[14] A Shimizu R Echigo S Hasegawa and M Hishida ldquoEx-perimental study on the pressure drop and the entry length ofthe gas-solid suspension flow in a circular tuberdquo InternationalJournal of Multiphase Flow vol 4 no 1 pp 53ndash64 1978

[15] N Guanhua D Kai L Shang and S Qian ldquoGas desorptioncharacteristics effected by the pulsating hydraulic fracturingin coalrdquo Fuel vol 236 pp 190ndash200 2019

[16] G Zhou Y Ma T Fan and G Wang ldquoPreparation andcharacteristics of a multifunctional dust suppressant withagglomeration and wettability performance used in coalminerdquo Chemical Engineering Research and Design vol 132pp 729ndash742 2018

[17] R D Marcus J D Hilbert Jr and G E Klinzing ldquoFlowthrough bends and acceleration zones in pneumatic con-veying systemsrdquo Bulk Solids Handling vol 5 no 4 pp 121ndash126 1985

[18] T Fan G Zhou and J Wang ldquoPreparation and character-ization of a wetting-agglomeration-based hybrid coal dustsuppressantrdquo Process Safety and Environmental Protectionvol 113 pp 282ndash291 2018

[19] R A Duckworth Empirical Correlations Fore Dilute PhaseDepartment of Chemical Engineering 1e University ofQueensland Brisbane Australia Lecture notes CSIROMineral engineering 1969

[20] Y Tomita and H Tashiro ldquoLoss coefficient for abrupt en-largement in pneumatic transport of solids in pipesrdquo BulkSolid Handling vol 8 pp 129ndash131 1988

[21] J A Ottjes ldquoDigital simulation of pneumatic particletransportrdquo Chemical Engineering Science vol 33 no 6pp 783ndash786 1978

[22] H V Nguyen R Yokota G Stenchikov et al ldquoA paralleldirect numerical simulation of dust particles in a turbulentflowrdquo in Proceedings of the EGU General Assembly ConferenceAbstracts Vienna Austria April 2012

[23] N Huber and M Sommerfeld ldquoModelling and numericalcalculation of dilute-phase pneumatic conveying in pipesystemsrdquo Powder Technology vol 99 no 1 pp 90ndash101 1998

[24] K J Hanley E P Byrne and K Cronin ldquoProbabilisticanalysis of particle impact at a pipe bend in pneumaticconveyingrdquo Powder Technology vol 233 pp 176ndash185 2013

[25] G E Klinzing and O M Basha ldquoA correlation for particlevelocities in pneumatic conveyingrdquo Powder Technologyvol 310 pp 201ndash204 2017

[26] H G Merkus and G M H Meesters ldquoProduction handlingand characterization of particulate materialsrdquo Particle Tech-nology vol 11 no 4 pp 619ndash629 2016

[27] G Liu W Cheng and L Chen ldquoInvestigating and optimizingthe mix proportion of pumping wet-mix shotcrete withpolypropylene fiberrdquo Construction and Building Materialsvol 150 pp 14ndash23 2017

[28] W Wei G Qingliang W Yuxin Y Hairui Z Jiansheng andL Junfu ldquoExperimental study on the solid velocity in hori-zontal dilute phase pneumatic conveying of fine powdersrdquoPowder Technology vol 212 no 3 pp 403ndash409 2011

[29] N M Tripathi A Levy and H Kalman ldquoAccelerationpressure drop analysis in horizontal dilute phase pneumaticconveying systemrdquo Powder Technology vol 327 pp 43ndash562018

[30] L Chen G Ma G Liu and Z Liu ldquoEffect of pumping andspraying processes on the rheological properties and aircontent of wet-mix shotcrete with various admixturesrdquoConstruction and Building Materials vol 225 pp 311ndash3232019

[31] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[32] B Kong E Wang W Lu and Z Li ldquoApplication of elec-tromagnetic radiation detection in high-temperature anom-alous areas experiencing coalfield firesrdquo Energy vol 189Article ID 116144 2019

10 Advances in Civil Engineering

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lines was 1m and the radius of the other two bent lines was06m To assure consistency of the concrete lines the bend ofthe line was fixed onto the self-made bend fixing device usingan ordinary rubber hose During line pavement horizon-tality and coaxial performance of concrete lines were verifiedby the rotating laser

22 Experimental Instruments Compressed air enters theshotcrete machine via the regulating valve and vortexshedding flowmeter to adjust and measure the input pres-sure and flow rate of compressed air In the present ex-periment the pressure drop in the concrete lines wasmeasured by a high-accuracy flat film pressure transmitter1e sensor applied the Dwyer FDT series of the flat filmpressure transmitter made by the Deville Company (USA)with a measuring range of 0ndash16MPa and an accuracy of002 According to the service manual of the sensor thepressure transmitter was installed on a section of the

specially made line and the concrete line was fixed onto arubber hose by a special pipe clamp To prevent scratches ofthe sensor by gravels a strainer was installed before thepressure transmitter (Figure 3)

1e temperature and flow rate of the compressed airwere measured by a vortex shedding flowmeter 1e tem-perature was viewed as constant throughout the conveyingof concrete Hence the temperature in the entire line wasequal to the inlet temperature 1e temperature of the mixedconcrete in all experiments was controlled between 15 and20degC

1e rotating speed of the chain wheel was 20 rminwhen the shotcrete machine reached the maximum de-livery capacity (6m3h) 1e feeding speed of the shotcretemachine could be adjusted by a transducer 1e vortexshedding flowmeter for measuring the flow rate ofcompressed air and the pressure transmitter for mea-suring pressure in the lines were read and data werereceived by the paperless recorder

Vortex street flowmeterPressure gauge

Blast pipe

Outlet

Shotcrete machine

Concrete linePressure transmitter

Figure 1 Structure of the PTS7 pushing chained shotcrete machine

Flow

R = 1m

R = 06m

R = 1mR = 06m

P-AP-B

P-CP-D

P-EP-1

P-2P-3

P-4P-5

P-6P-7

P-8P-9

Pmdash1Pressure transducer numberNotation for pressure transducer

2m typical dist

Figure 2 Structure of concrete lines

Advances in Civil Engineering 3

23 Experimental Materials

231 Cement 1e cement used in the experiments wasPO425 cement made by the Shandong Shanshui CementGroup Its purity and specific gravity were 3100 cm2g and314 respectively

232 Aggregates Aggregates can be divided into fine andcoarse aggregates 1e former used natural river sands Afterscreening its fineness modulus silt content and apparentdensity were 275 12 and 268 gcm3 respectively 1ecoarse aggregate applied was ordinary limestone fragmentswhose maximum grain size was less than 10mm Contin-uous grading was performed to remove impurities beforemixing the fine and coarse aggregates 1e grading curves offine and coarse aggregates are shown in Figure 4 and theyconform to limitations of recommended grades in the na-tional standard GB50086-2001 [27]

233 Chemical Admixture 1e main chemical admixturein this experiment was accelerator 1is accelerator was akind of powdery solid with density 4 gcm3

234 Concrete Ratio In the experiment the concrete wasmade up according to the common concrete ratio in the coalmine Also the concrete ratio was cement fine aggregates coarse aggregates accelerator 1 2 2 003

3 Experimental and Analysis Methods

1e PTS7 pushing chained shotcrete machine used in theexperiments can achieve material feeding at a constant speedby motor-driven piston motion 1e prediction of thepressure drop during wind-driven conveying of concretepredicts the pressure drop in unit length In concrete linesthe acceleration process of concrete mainly distributes at the

initial conveying section and after passing the bent line 1eeffects of these acceleration processes are identical 1ere-fore attention was given to the pressure drop during theacceleration processes of concrete in the initial section andafter passing the bent line in the experiments

In the pressure drop test during concrete conveying thepressure in the concrete lines must be measured To preventscratches on the pressure transmitter from the gravels theexperiment was performed using the following method

Before the commencement of the experiment theconcrete lines were verified by only supplying compressedair

(1) Figure 3(a) shows that without the strainer thebottom of the pressure transmitter was installed ontothe inner wall of the concrete lines 1e compressedair was supplied and the pressure at different po-sitions along the line was recorded by pressuretransmitters 1is is the universal method for thepressure transmitter and it can accurately measurethe pressure in concrete lines

Transducer rider

Pressure transducer

Adjusting nut

(a)

Transducer rider

Pressure transducer

Adjusting nut Strainer

(b)

Figure 3 Installation structure of the pressure transmitter on lines (a) Standard installation structure of the pressure transmitter (b)Installation structure of the pressure transmitter with strainer

Fine agg limitsCoarse agg limitsGravel gradation

Perc

enta

ge p

asse

d by

wei

ght (

)

Sand gradation

0

40

20

60

80

100

10 10010Sieve size (mm)

Figure 4 Grade curves of fine and coarse aggregates

4 Advances in Civil Engineering

(2) In Figure 3(b) a strainer was placed on the mountingbase of the pressure transmitter Later the pressuretransmitter was installed to keep the bottom of thepressure transmitter 2mm away from the strainerCompressed air was supplied and pressures along theconcrete line were recorded by the pressure transmitter

Pressures under the above two conditions aresummarized in Figure 5 During this process thepressures at the different positions that were measuredby the two methods had a fixed difference of ΔP0 Whenthe pressure in the concrete conveying was measured bythe method in Figure 3(b) the pressure in the concreteline was equal to the sum of the measured pressure P0and ΔP0 In other words pressure changes after theaddition of a strainer could be used to reflect thepressure changes in the concrete lines throughoutconveying

1e acceleration pressure drop in the horizontal sectionof the concrete conveying was mainly caused by the meanpressure difference measured by the pressure transmitter1e measured acceleration pressure drop between any twopoints in the analysis region was discussed Howeverwhether concrete was in the initial section or had passed thebent line was neglected thus it was believed that the mo-mentum and energy changes were the same given the samevelocity changes

During the experiment pressure drop in the acceleratezone occurred as shown in Figure 6 1e pressure dropcurve shows that the pressure drop in the accelerate zonereached a relatively stable trend 1e pressure curveduring this process was fitted and a straight line repre-senting the steady-state pressure drop was deduced basedon the final process of the stable pressure drop Based onthis deduced straight line the pressure at zero speed couldbe determined

In Figure 6 ΔPacctotal is the total pressure drop in theaccelerate zone and ΔPacc is the acceleration pressure dropof concrete

According to reverse deduction from the stable value ofthe above curves energy loss under steady state can beobtained from the index trend and linear pressure gradienttrend of floating points leading to the acceleration ofpressure drop and thus obtaining the actual pressure droptrend An exponential linear equation was fitted by thepressure fitting curve in Figure 6

P0 p1 middot eminus xp2 + p3 middot x + p4 (3)

Here x is the length of the test section and p1 p2 p3 andp4 are constants 1e numerical value in Figure 6 wasbrought into equation (3) thus obtaining the followingequation

P0 11 middot eminus 036x

minus 45x + 307 (4)

1is pressure-distance relation equation covers twoparts (1) p1 middot eminus xp2 is the exponential function that reflectsthe pressure drop caused by the acceleration in the concreteline (2) p3 middot x + p4 is the linear function that reflects the

pressure drop caused by concrete collision and friction in theline Under this circumstance the pressure drop is dis-tributed uniformly Based on the above curves we can obtainthe following results

(a) Steady pressure drop in the concrete line(b) Accelerated pressure drop in the concrete line(c) 1e pressure at the beginning of acceleration is

difficult to measure Under this circumstance thepressure at the beginning of acceleration can bededuced by the equation 1us the pressure dropfrom zero to a steady speed could be calculated

(d) Length of the accelerate zone (part 1 in the equationis approaching zero)

To predict the length of the accelerate zone duringconcrete conveying Wei et al introduced the Archimedesnumber [28] 1e Archimedes number mainly reflects theratio between buoyancy and viscosity force and can beexpressed as

∆P

With strainerWithout strainer

260

270

280

290

300

310

320

330

340

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

Figure 5 Effects of the strainer in the pressure transmitter on thegas-phase pressure drop

Steady-statepressure drop

trendPressure point

Actual pressuredrop trend

Accelerate zone

Accelerate length

Steady-statezone

∆Pacc

∆Pacc total

∆Pss

260

270

280

290

300

310

320Pr

essu

re (k

Pa)

12106 8 14 162 4 18 200Distance (m)

Figure 6 Trend of pressure drop during concrete conveying

Advances in Civil Engineering 5

Ar ρc minus ρf( 1113857g middot d3

v2 middot ρf (5)

where Ar is the Archimedes number ρc is the density ofconcrete ρf is the density of air v is the kinematic viscosityand d is the mean diameter of concrete particles

In the present study the conveying speed of theconcrete particles was measured with a high-speedcamera Pressure changes in the concrete line weremeasured by the pressure transmitter 1e length of theaccelerate zone of concrete was expressed by particlespeed and pressure changes Moreover the relation be-tween the Archimedes number and length of the accel-erate zone was expressed as

Lacc 16Ar01 (6)

During the present experiment the total pressure dropin the accelerate zone was expressed as the sum of steady-state pressure drop and accelerated pressure drop (equation(7))1e accelerated pressure drop (ΔPacc) is the momentumequation of concrete and can be expressed as equation (8)

ΔPacctotal ΔPss + ΔPacc (7)

ΔPacc ΔPmom _msΔuc

A

_ms ucss minus 0( 1113857

A (8)

where ΔPacctotal is the total pressure drop of the acceleratezone ΔPacc is the accelerated pressure drop of concrete ΔPssis the constant pressure drop of concrete and _ms is the massvelocity of concrete particle flow

1e total pressure drop in equation (7)was used to calculatethe derivation of displacement and can be expressed as

dPacctotal

dxdPss

dx+dPacc

dx (9)

To analyze the steady-state speed and transient speedduring concrete conveying an equation was constructed inthe present experiment with reference to the study by Weiet al [28]

ucss

uf 1 minus 0072 Ar middot

ρc minus ρfv2 middot ρf

1113890 1113891

0091

(10)

uc

ucss 1 minus e

minus 48xLacc (11)

where ucss is the steady speed of concrete uc is the initialvelocity of concrete and uf is the air velocity 1e derivativeof distance was calculated based on equation (10) and wasbrought into equation (11)

dPacctotal

dxdPss

dx+

_ms

A

duc

dx (12)

1e value of uc in equation (8) was brought into equation(12) to obtain

dPacctotal

dxdPss

dx+

_ms middot ucss

A

duc

dx1 minus e

minus 48xLacc1113872 1113873 (13)

Based on the integration of the displacement x throughequation (13) the following was obtained

1113946Lacc

0

dPacctotal

dx1113888 1113889dx 1113946

Lacc

0

dPss

dx1113888 1113889dx minus 1113946

Lacc

0

_ms middot ucss

A

48Lacc

1 minus eminus 48xLacc1113872 1113873dx

(14)

1erefore

Ptotal _ms

Aucss middot e

minus 48Lacc( )x+ p3 middot x + p4 (15)

By comparing equations (3) and (15) the following wasobtained

p1 _ms

Aucss

p2 minus48Lacc

x

(16)

1us the accelerated pressure drop of concrete can beexpressed as

ΔPacc _ms

Aucss middot e

minus 48Lacc( )x

_ms

Aucss middot e

minus 4816Ar01( )x

_ms

Aucss

middot eminus 4816 ρcminus ρf( )gmiddotd3( ) v2 middotρf( )( )

01( 1113857x

(17)

To protect the accuracy of the conclusions the concreteflow trend in the constant speed section was verified bychanging the supply quantity of concrete and air input 1estarting point of the constant speed section was set at 15mafter the bent line In the experiment the concrete supplywas controlled by the rotating speed of the motor of thetransducer During this process the relationship between thepressure drop during concrete conveying and concretesupply was found as shown in Figure 71e figure shows theeffects of air flow and concrete supply quantity on pressuredrop during the conveying of concrete

However equation (7) focused on testing the physicalproperty of the accelerated pressure drop which is the re-lationship between the momentum equation and pneumatictransmission during the conveying of concrete To accuratelypredict the relationship of accelerated pressure drop in theconveying of concrete the correction factor αwas introduced toincrease the prediction accuracy 1erefore the prediction ofthe total pressure drop in the acceleration zonewas calculated as

ΔPacctotal αΔPss + ΔPacc (18)

4 Results and Discussions

It is very simple to predict the pressure drop during concreteconveying by experiments First it must be determined thatthe pressure drop during concrete conveying is caused byaccelerated conveying friction and the collision of con-cretes 1e pressure drop caused by the acceleration of

6 Advances in Civil Engineering

concrete is also called the accelerated pressure drop and itonly exists in the accelerate zone 1e pressure dropcaused by friction and collision is called the uniformpressure drop and it exists throughout the conveying ofconcrete 1erefore the pressure drop caused by accel-eration can be calculated by the accelerated pressure dropminus the uniform pressure In the calculation of pressuredrop during concrete conveying the sum of steady-statepressure drop and accelerated pressure drop is the totalpressure drop in the accelerate zone 1is relationship isbased on the hypothesis that the steady-state pressuredrop in the accelerate zone and constant speed section arethe same

When predicting the pressure drop during concreteconveying the accelerated pressure drop can be predictedby equation (8) Hence the steady-state speed in theconveying of concrete must be known which can be cal-culated by equations (10) and (11) During the presentexperiment the rotating speed of the motor was changed bythe transducer thus changing the mass flow rate duringconcrete conveying Simultaneously the pressures at dif-ferent positions in the accelerate zone and constant speedzone could be measured

1e experimental pressure drop trend of concrete underdifferent mass flow rates is shown in Figure 8 which iscomparing the curves drawn based on equation (17) Fig-ure 8 shows that the increasing trend of the curves underdifferent supply quantities of concrete is the same Based onthe comparison of the curves drawn in accordance withFigure 8 the theoretical trend might overlap with the actualcurve measured in the experiment If these two curvesoverlap then the actual pressure drop during concreteconveying is similar to the predicted pressure drop provingthe accuracy of the prediction If the actual pressure dropdoes not overlap with the predicted pressure drop thesteady-state pressure drop in the accelerate zone is differentfrom that in the constant speed zone

1e effects of concrete pressure (p0) at the beginningposition on the pressure drop trend along the concreteconveying are shown in Figure 9 Normalization of pressureduring concrete conveying based on p0 can decrease theinfluence of the air flow rate on the pressure measurementand the maximum error can be controlled within 2

During multiple experimental processes the value of αwas calculated by changing the air flow rate and feeding rateof concrete under different motor speeds

Accelerated pressure drop and uniform pressure dropduring the concrete conveying were predicted based on thevalue of α If α 1 the pressure drop caused by concretecollision and friction was the same in the constant speedsection If αlt 1 the pressure drop was relatively small be-cause of the low conveying speed of concrete In contrastαgt 1 indicates a high pressure drop because of the highconveying speed of concrete In the constant speed section ofconcrete particle collision was weak However particlecollision frequency was high and particle collision wasstrong in the accelerate zone resulting in the high energyloss of concrete particles 1erefore the pressure drop in theaccelerate zone was higher than that in the constant speedsection

1e difference between the experimental and theoreticalresults of concrete conveying was positively related to theconcrete throughput given the same flow rate of compressedair When the concrete throughput was small the experi-mental results and theoretical results were similar indicatingthat α was closer to 1 (Figure 10) With an increase ofconcrete throughput the difference of experimental andtheoretical results gradually increased 1e difference is thekey factor influencing the prediction of concrete conveying

Next the value of the transducer was fixed and theconcrete was input by the shotcrete machine at a constantfeeding rate Subsequently pressures at different points weretested by controlling the input of compressed air with the

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h

6m3h

Figure 8 Variation trend of concrete pressure

Stea

dy-s

tate

pre

ssur

e dro

p pe

run

it le

ngth

(Pa

m)

Concrete throughput4m3h5m3h6m3h

0

500

1000

1500

2000

2500

3000

38 42 46 50 54 58 62 66 7034Air flow rate (m3min)

Figure 7 Variations of pressure drop in the constant speed sectionwith air flow

Advances in Civil Engineering 7

regulating valve 1ere was a large difference between theexperimental results and theoretical results With an in-crease of air flow rate such differences decreased gradually1is difference was also a key factor that influenced theprediction of concrete conveying

Figures 10 and 11 show that the value of α had a directrelationship with concrete throughput and input of com-pressed air Tripathi et al tested materials of different grainsizes [29] and α can be defined as

α a + b middot eminus cmiddotμ

( 1113857 (19)

where μ mcmf is the ratio of concrete mass and air massExperimental data from Figures 11 and 12 were brought

into equation (19) yielding the following

α 12 + 011eminus 09μ

1113872 1113873 (20)

During the accelerated pressure drop experiment theconveying of concrete particles was accelerated at a specificspeed from one point and finally reached the movementtrend at a constant speed [30ndash32] 1e momentum equationwas used to calculate the pressure drop during this process

ΔPacc ΔPmom _ms middot Δuc

A

_ms middot ucss minus uc( 1113857

A (21)

Pressure drop is at equilibrium in the constant speedsection 1erefore the total accelerated pressure drop can begained from equations (18) (19) and (21) 1e totalaccelerated pressure drop was expressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961ΔPss +_ms middot ucss minus uc( 1113857

A

(22)

Also equations (1) and (2) were brought into equation(22) and thus the total accelerated pressure drop wasexpressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961 fDρfu2

f2D

L + ΔPc1113888 1113889

+_ms middot ucss minus uc( 1113857

A

(23)

To verify the accuracy of equation (20) the feedingrate of concrete was kept constant in the experiment 1econcrete-air ratio was changed by altering the air flow rateto analyze the pressure at different positions along theline Comparison between theoretical and experimental

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

65m3h

Figure 10 Comparison of theoretical and experimental pressuresafter adding α

Air flow

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

7m3min65m3min6m3min

55m3min

Figure 11 Comparison of pressure drop in the accelerate zone

ndash22

Air flowTheoretical trendExperimental trendError range

04

05

06

07

08

09

10

PP 0

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

Figure 9 Normalization trend under different wind speeds

8 Advances in Civil Engineering

pressures is shown in Figure 12 1e curve equationgained from the theoretical formula was similar to theexperimental results showing a maximum error of lessthan 10 1is verified the universality of equation (20)In this experiment pipe diameters of 20 inches and 25inches of the concrete line were applied Pressures atdifferent positions of the concrete line were tested by apressure transmitter (Figure 12) 1e maximum error wasless than 5 verifying the feasibility of equation (20)

5 Conclusions

In order to obtain the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying the concreteconveying pipeline was arranged to conduct the relatedconcrete conveying experiment 1e concrete was made upaccording to the common concrete ratio in the coal mineEach point pressure on the pipeline during the progress ofconveying was tested by the pressure transmitter set up onthe pipeline Also the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying was analyzed withmeasured pressure

1e results show that the pipeline pressure droppedrapidly at the beginning of the conveying and at the end ofthe bending pipe and the trend of the dropping linearly wasshowed gradually 1e accelerated pressure drop was ana-lyzed by combining experimental and momentum equationsduring concrete conveying 1e accelerated pressure dropwas analyzed which was mainly caused by accelerationfriction and the collision of concretes Also the friction andthe collision of concretes also exist in the zone of stableconvey

1e pressure drop curve was drawn according to thepressure at each point in the concrete conveying processAlso the mathematical model of pressure drop in theconcrete conveying process was set up To prevent random

interference factor from the friction and the collision andimproving the calculation accuracy the correction factor αwas introduced

Finally the measured pressures under different concretethroughputs and flow rates of compressed air were com-pared with the results from the mathematical model whichverified the accuracy of the mathematical model Also themain factors of pressure drop in the accelerate zone wereobtained as the ratio of the concrete mass and the com-pressed mass the initial velocity of the concrete the optimalfinal required velocity the feed speed of concrete and crosssection area of the conveying pipeline

Data Availability

1e data used to support the findings of this study areavailable from the corresponding author upon request

Additional Points

Innovations and highlights (1) Damage to the pressuretransmitter by concrete can be prevented by installing astrainer before the pressure transmitter (2) Variation laws ofpressure before and after the installation of a pressuretransmitter were studied by supplying air only (3) A sta-tistical analysis of the pressures at different positions alongthe concrete conveying line under different input quantitiesof concrete and compressed air was performed Based onthis the law of pressure drop during the conveying ofconcrete was discussed (4) 1e pressure drop in the lineduring the conveying of concrete was predicted

Conflicts of Interest

1e authors declare that they have no conflicts of interest

References

[1] L Chen G LiuW Cheng and G Pan ldquoPipe flow of pumpingwet shotcrete based on lubrication layerrdquo SpringerPlus vol 5no 1 p 945 2016

[2] Y Cai Y Jiang I Djamaluddin T Iura and T Esaki ldquoAnanalytical model considering interaction behavior of groutedrock bolts for convergence-confinement method in tunnelingdesignrdquo International Journal of Rock Mechanics and MiningSciences vol 76 pp 112ndash126 2015

[3] L Chen P Li G Liu W Cheng and Z Liu ldquoDevelopment ofcement dust suppression technology during shotcrete in mineof China-a reviewrdquo Journal of Loss Prevention in the ProcessIndustries vol 55 pp 232ndash242 2018

[4] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[5] Q Liu W Nie Y Hua H Peng and Z Liu ldquo1e effects of theinstallation position of a multi-radial swirling air-curtaingenerator on dust diffusion and pollution rules in a fully-mechanized excavation face a case studyrdquo Powder Technol-ogy vol 329 pp 371ndash385 2018

[6] R Naveh N M Tripathi and H Kalman ldquoExperimentalpressure drop analysis for horizontal dilute phase particle-fluid flowsrdquo Powder Technology vol 321 pp 353ndash368 2017

Pipe diameter

3

2inch25inch

Theoretical trendExperimental trend

5

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

Figure 12 Pressure drop at different specifications of concretelines

Advances in Civil Engineering 9

[7] O G Brown ldquo1e history of the Darcy-Weisbach equationfor pipe flow resistancerdquo in Proceedings of the Environmentaland Water Resources History pp 34ndash43 Washington DCUSA November 2003

[8] O Molerus ldquoOverview pneumatic transport of solidsrdquoPowder Technology vol 88 no 3 pp 309ndash321 1996

[9] Q LiuW Nie Y Hua H Peng C Liu and CWei ldquoResearchon tunnel ventilation systems dust diffusion and pollutionbehaviour by air curtains based on CFD technology and fieldmeasurementrdquo Building and Environment vol 147pp 444ndash460 2019

[10] Y-Q Zhang J-L Zhu X-H Wang X-W ZhangS-X Zhou and P Liang ldquoSimulation of large coal particlespyrolysis by circulating ash heat carrier toward the axialdimension of the moving bedrdquo Fuel Processing Technologyvol 154 pp 227ndash234 2016

[11] Y Tomita H Tashiro K Deguchi and T Jotaki ldquoSuddenexpansion of gas-solid two-phase flow in a piperdquo Physics ofFluids vol 23 no 4 pp 663ndash666 1980

[12] P Li Z Zhou L Chen G Liu and W Xiao ldquoResearch ondust suppression technology of shotcrete based on new sprayequipment and process optimizationrdquo Advances in CivilEngineering vol 2019 Article ID 4831215 11 pages 2019

[13] B Kong E Wang and Z Li ldquo1e effect of high temperatureenvironment on rock propertiesmdashan example of electro-magnetic radiation characterizationrdquo Environmental Scienceand Pollution Research vol 25 no 29 pp 1ndash11 2018

[14] A Shimizu R Echigo S Hasegawa and M Hishida ldquoEx-perimental study on the pressure drop and the entry length ofthe gas-solid suspension flow in a circular tuberdquo InternationalJournal of Multiphase Flow vol 4 no 1 pp 53ndash64 1978

[15] N Guanhua D Kai L Shang and S Qian ldquoGas desorptioncharacteristics effected by the pulsating hydraulic fracturingin coalrdquo Fuel vol 236 pp 190ndash200 2019

[16] G Zhou Y Ma T Fan and G Wang ldquoPreparation andcharacteristics of a multifunctional dust suppressant withagglomeration and wettability performance used in coalminerdquo Chemical Engineering Research and Design vol 132pp 729ndash742 2018

[17] R D Marcus J D Hilbert Jr and G E Klinzing ldquoFlowthrough bends and acceleration zones in pneumatic con-veying systemsrdquo Bulk Solids Handling vol 5 no 4 pp 121ndash126 1985

[18] T Fan G Zhou and J Wang ldquoPreparation and character-ization of a wetting-agglomeration-based hybrid coal dustsuppressantrdquo Process Safety and Environmental Protectionvol 113 pp 282ndash291 2018

[19] R A Duckworth Empirical Correlations Fore Dilute PhaseDepartment of Chemical Engineering 1e University ofQueensland Brisbane Australia Lecture notes CSIROMineral engineering 1969

[20] Y Tomita and H Tashiro ldquoLoss coefficient for abrupt en-largement in pneumatic transport of solids in pipesrdquo BulkSolid Handling vol 8 pp 129ndash131 1988

[21] J A Ottjes ldquoDigital simulation of pneumatic particletransportrdquo Chemical Engineering Science vol 33 no 6pp 783ndash786 1978

[22] H V Nguyen R Yokota G Stenchikov et al ldquoA paralleldirect numerical simulation of dust particles in a turbulentflowrdquo in Proceedings of the EGU General Assembly ConferenceAbstracts Vienna Austria April 2012

[23] N Huber and M Sommerfeld ldquoModelling and numericalcalculation of dilute-phase pneumatic conveying in pipesystemsrdquo Powder Technology vol 99 no 1 pp 90ndash101 1998

[24] K J Hanley E P Byrne and K Cronin ldquoProbabilisticanalysis of particle impact at a pipe bend in pneumaticconveyingrdquo Powder Technology vol 233 pp 176ndash185 2013

[25] G E Klinzing and O M Basha ldquoA correlation for particlevelocities in pneumatic conveyingrdquo Powder Technologyvol 310 pp 201ndash204 2017

[26] H G Merkus and G M H Meesters ldquoProduction handlingand characterization of particulate materialsrdquo Particle Tech-nology vol 11 no 4 pp 619ndash629 2016

[27] G Liu W Cheng and L Chen ldquoInvestigating and optimizingthe mix proportion of pumping wet-mix shotcrete withpolypropylene fiberrdquo Construction and Building Materialsvol 150 pp 14ndash23 2017

[28] W Wei G Qingliang W Yuxin Y Hairui Z Jiansheng andL Junfu ldquoExperimental study on the solid velocity in hori-zontal dilute phase pneumatic conveying of fine powdersrdquoPowder Technology vol 212 no 3 pp 403ndash409 2011

[29] N M Tripathi A Levy and H Kalman ldquoAccelerationpressure drop analysis in horizontal dilute phase pneumaticconveying systemrdquo Powder Technology vol 327 pp 43ndash562018

[30] L Chen G Ma G Liu and Z Liu ldquoEffect of pumping andspraying processes on the rheological properties and aircontent of wet-mix shotcrete with various admixturesrdquoConstruction and Building Materials vol 225 pp 311ndash3232019

[31] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[32] B Kong E Wang W Lu and Z Li ldquoApplication of elec-tromagnetic radiation detection in high-temperature anom-alous areas experiencing coalfield firesrdquo Energy vol 189Article ID 116144 2019

10 Advances in Civil Engineering

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23 Experimental Materials

231 Cement 1e cement used in the experiments wasPO425 cement made by the Shandong Shanshui CementGroup Its purity and specific gravity were 3100 cm2g and314 respectively

232 Aggregates Aggregates can be divided into fine andcoarse aggregates 1e former used natural river sands Afterscreening its fineness modulus silt content and apparentdensity were 275 12 and 268 gcm3 respectively 1ecoarse aggregate applied was ordinary limestone fragmentswhose maximum grain size was less than 10mm Contin-uous grading was performed to remove impurities beforemixing the fine and coarse aggregates 1e grading curves offine and coarse aggregates are shown in Figure 4 and theyconform to limitations of recommended grades in the na-tional standard GB50086-2001 [27]

233 Chemical Admixture 1e main chemical admixturein this experiment was accelerator 1is accelerator was akind of powdery solid with density 4 gcm3

234 Concrete Ratio In the experiment the concrete wasmade up according to the common concrete ratio in the coalmine Also the concrete ratio was cement fine aggregates coarse aggregates accelerator 1 2 2 003

3 Experimental and Analysis Methods

1e PTS7 pushing chained shotcrete machine used in theexperiments can achieve material feeding at a constant speedby motor-driven piston motion 1e prediction of thepressure drop during wind-driven conveying of concretepredicts the pressure drop in unit length In concrete linesthe acceleration process of concrete mainly distributes at the

initial conveying section and after passing the bent line 1eeffects of these acceleration processes are identical 1ere-fore attention was given to the pressure drop during theacceleration processes of concrete in the initial section andafter passing the bent line in the experiments

In the pressure drop test during concrete conveying thepressure in the concrete lines must be measured To preventscratches on the pressure transmitter from the gravels theexperiment was performed using the following method

Before the commencement of the experiment theconcrete lines were verified by only supplying compressedair

(1) Figure 3(a) shows that without the strainer thebottom of the pressure transmitter was installed ontothe inner wall of the concrete lines 1e compressedair was supplied and the pressure at different po-sitions along the line was recorded by pressuretransmitters 1is is the universal method for thepressure transmitter and it can accurately measurethe pressure in concrete lines

Transducer rider

Pressure transducer

Adjusting nut

(a)

Transducer rider

Pressure transducer

Adjusting nut Strainer

(b)

Figure 3 Installation structure of the pressure transmitter on lines (a) Standard installation structure of the pressure transmitter (b)Installation structure of the pressure transmitter with strainer

Fine agg limitsCoarse agg limitsGravel gradation

Perc

enta

ge p

asse

d by

wei

ght (

)

Sand gradation

0

40

20

60

80

100

10 10010Sieve size (mm)

Figure 4 Grade curves of fine and coarse aggregates

4 Advances in Civil Engineering

(2) In Figure 3(b) a strainer was placed on the mountingbase of the pressure transmitter Later the pressuretransmitter was installed to keep the bottom of thepressure transmitter 2mm away from the strainerCompressed air was supplied and pressures along theconcrete line were recorded by the pressure transmitter

Pressures under the above two conditions aresummarized in Figure 5 During this process thepressures at the different positions that were measuredby the two methods had a fixed difference of ΔP0 Whenthe pressure in the concrete conveying was measured bythe method in Figure 3(b) the pressure in the concreteline was equal to the sum of the measured pressure P0and ΔP0 In other words pressure changes after theaddition of a strainer could be used to reflect thepressure changes in the concrete lines throughoutconveying

1e acceleration pressure drop in the horizontal sectionof the concrete conveying was mainly caused by the meanpressure difference measured by the pressure transmitter1e measured acceleration pressure drop between any twopoints in the analysis region was discussed Howeverwhether concrete was in the initial section or had passed thebent line was neglected thus it was believed that the mo-mentum and energy changes were the same given the samevelocity changes

During the experiment pressure drop in the acceleratezone occurred as shown in Figure 6 1e pressure dropcurve shows that the pressure drop in the accelerate zonereached a relatively stable trend 1e pressure curveduring this process was fitted and a straight line repre-senting the steady-state pressure drop was deduced basedon the final process of the stable pressure drop Based onthis deduced straight line the pressure at zero speed couldbe determined

In Figure 6 ΔPacctotal is the total pressure drop in theaccelerate zone and ΔPacc is the acceleration pressure dropof concrete

According to reverse deduction from the stable value ofthe above curves energy loss under steady state can beobtained from the index trend and linear pressure gradienttrend of floating points leading to the acceleration ofpressure drop and thus obtaining the actual pressure droptrend An exponential linear equation was fitted by thepressure fitting curve in Figure 6

P0 p1 middot eminus xp2 + p3 middot x + p4 (3)

Here x is the length of the test section and p1 p2 p3 andp4 are constants 1e numerical value in Figure 6 wasbrought into equation (3) thus obtaining the followingequation

P0 11 middot eminus 036x

minus 45x + 307 (4)

1is pressure-distance relation equation covers twoparts (1) p1 middot eminus xp2 is the exponential function that reflectsthe pressure drop caused by the acceleration in the concreteline (2) p3 middot x + p4 is the linear function that reflects the

pressure drop caused by concrete collision and friction in theline Under this circumstance the pressure drop is dis-tributed uniformly Based on the above curves we can obtainthe following results

(a) Steady pressure drop in the concrete line(b) Accelerated pressure drop in the concrete line(c) 1e pressure at the beginning of acceleration is

difficult to measure Under this circumstance thepressure at the beginning of acceleration can bededuced by the equation 1us the pressure dropfrom zero to a steady speed could be calculated

(d) Length of the accelerate zone (part 1 in the equationis approaching zero)

To predict the length of the accelerate zone duringconcrete conveying Wei et al introduced the Archimedesnumber [28] 1e Archimedes number mainly reflects theratio between buoyancy and viscosity force and can beexpressed as

∆P

With strainerWithout strainer

260

270

280

290

300

310

320

330

340

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

Figure 5 Effects of the strainer in the pressure transmitter on thegas-phase pressure drop

Steady-statepressure drop

trendPressure point

Actual pressuredrop trend

Accelerate zone

Accelerate length

Steady-statezone

∆Pacc

∆Pacc total

∆Pss

260

270

280

290

300

310

320Pr

essu

re (k

Pa)

12106 8 14 162 4 18 200Distance (m)

Figure 6 Trend of pressure drop during concrete conveying

Advances in Civil Engineering 5

Ar ρc minus ρf( 1113857g middot d3

v2 middot ρf (5)

where Ar is the Archimedes number ρc is the density ofconcrete ρf is the density of air v is the kinematic viscosityand d is the mean diameter of concrete particles

In the present study the conveying speed of theconcrete particles was measured with a high-speedcamera Pressure changes in the concrete line weremeasured by the pressure transmitter 1e length of theaccelerate zone of concrete was expressed by particlespeed and pressure changes Moreover the relation be-tween the Archimedes number and length of the accel-erate zone was expressed as

Lacc 16Ar01 (6)

During the present experiment the total pressure dropin the accelerate zone was expressed as the sum of steady-state pressure drop and accelerated pressure drop (equation(7))1e accelerated pressure drop (ΔPacc) is the momentumequation of concrete and can be expressed as equation (8)

ΔPacctotal ΔPss + ΔPacc (7)

ΔPacc ΔPmom _msΔuc

A

_ms ucss minus 0( 1113857

A (8)

where ΔPacctotal is the total pressure drop of the acceleratezone ΔPacc is the accelerated pressure drop of concrete ΔPssis the constant pressure drop of concrete and _ms is the massvelocity of concrete particle flow

1e total pressure drop in equation (7)was used to calculatethe derivation of displacement and can be expressed as

dPacctotal

dxdPss

dx+dPacc

dx (9)

To analyze the steady-state speed and transient speedduring concrete conveying an equation was constructed inthe present experiment with reference to the study by Weiet al [28]

ucss

uf 1 minus 0072 Ar middot

ρc minus ρfv2 middot ρf

1113890 1113891

0091

(10)

uc

ucss 1 minus e

minus 48xLacc (11)

where ucss is the steady speed of concrete uc is the initialvelocity of concrete and uf is the air velocity 1e derivativeof distance was calculated based on equation (10) and wasbrought into equation (11)

dPacctotal

dxdPss

dx+

_ms

A

duc

dx (12)

1e value of uc in equation (8) was brought into equation(12) to obtain

dPacctotal

dxdPss

dx+

_ms middot ucss

A

duc

dx1 minus e

minus 48xLacc1113872 1113873 (13)

Based on the integration of the displacement x throughequation (13) the following was obtained

1113946Lacc

0

dPacctotal

dx1113888 1113889dx 1113946

Lacc

0

dPss

dx1113888 1113889dx minus 1113946

Lacc

0

_ms middot ucss

A

48Lacc

1 minus eminus 48xLacc1113872 1113873dx

(14)

1erefore

Ptotal _ms

Aucss middot e

minus 48Lacc( )x+ p3 middot x + p4 (15)

By comparing equations (3) and (15) the following wasobtained

p1 _ms

Aucss

p2 minus48Lacc

x

(16)

1us the accelerated pressure drop of concrete can beexpressed as

ΔPacc _ms

Aucss middot e

minus 48Lacc( )x

_ms

Aucss middot e

minus 4816Ar01( )x

_ms

Aucss

middot eminus 4816 ρcminus ρf( )gmiddotd3( ) v2 middotρf( )( )

01( 1113857x

(17)

To protect the accuracy of the conclusions the concreteflow trend in the constant speed section was verified bychanging the supply quantity of concrete and air input 1estarting point of the constant speed section was set at 15mafter the bent line In the experiment the concrete supplywas controlled by the rotating speed of the motor of thetransducer During this process the relationship between thepressure drop during concrete conveying and concretesupply was found as shown in Figure 71e figure shows theeffects of air flow and concrete supply quantity on pressuredrop during the conveying of concrete

However equation (7) focused on testing the physicalproperty of the accelerated pressure drop which is the re-lationship between the momentum equation and pneumatictransmission during the conveying of concrete To accuratelypredict the relationship of accelerated pressure drop in theconveying of concrete the correction factor αwas introduced toincrease the prediction accuracy 1erefore the prediction ofthe total pressure drop in the acceleration zonewas calculated as

ΔPacctotal αΔPss + ΔPacc (18)

4 Results and Discussions

It is very simple to predict the pressure drop during concreteconveying by experiments First it must be determined thatthe pressure drop during concrete conveying is caused byaccelerated conveying friction and the collision of con-cretes 1e pressure drop caused by the acceleration of

6 Advances in Civil Engineering

concrete is also called the accelerated pressure drop and itonly exists in the accelerate zone 1e pressure dropcaused by friction and collision is called the uniformpressure drop and it exists throughout the conveying ofconcrete 1erefore the pressure drop caused by accel-eration can be calculated by the accelerated pressure dropminus the uniform pressure In the calculation of pressuredrop during concrete conveying the sum of steady-statepressure drop and accelerated pressure drop is the totalpressure drop in the accelerate zone 1is relationship isbased on the hypothesis that the steady-state pressuredrop in the accelerate zone and constant speed section arethe same

When predicting the pressure drop during concreteconveying the accelerated pressure drop can be predictedby equation (8) Hence the steady-state speed in theconveying of concrete must be known which can be cal-culated by equations (10) and (11) During the presentexperiment the rotating speed of the motor was changed bythe transducer thus changing the mass flow rate duringconcrete conveying Simultaneously the pressures at dif-ferent positions in the accelerate zone and constant speedzone could be measured

1e experimental pressure drop trend of concrete underdifferent mass flow rates is shown in Figure 8 which iscomparing the curves drawn based on equation (17) Fig-ure 8 shows that the increasing trend of the curves underdifferent supply quantities of concrete is the same Based onthe comparison of the curves drawn in accordance withFigure 8 the theoretical trend might overlap with the actualcurve measured in the experiment If these two curvesoverlap then the actual pressure drop during concreteconveying is similar to the predicted pressure drop provingthe accuracy of the prediction If the actual pressure dropdoes not overlap with the predicted pressure drop thesteady-state pressure drop in the accelerate zone is differentfrom that in the constant speed zone

1e effects of concrete pressure (p0) at the beginningposition on the pressure drop trend along the concreteconveying are shown in Figure 9 Normalization of pressureduring concrete conveying based on p0 can decrease theinfluence of the air flow rate on the pressure measurementand the maximum error can be controlled within 2

During multiple experimental processes the value of αwas calculated by changing the air flow rate and feeding rateof concrete under different motor speeds

Accelerated pressure drop and uniform pressure dropduring the concrete conveying were predicted based on thevalue of α If α 1 the pressure drop caused by concretecollision and friction was the same in the constant speedsection If αlt 1 the pressure drop was relatively small be-cause of the low conveying speed of concrete In contrastαgt 1 indicates a high pressure drop because of the highconveying speed of concrete In the constant speed section ofconcrete particle collision was weak However particlecollision frequency was high and particle collision wasstrong in the accelerate zone resulting in the high energyloss of concrete particles 1erefore the pressure drop in theaccelerate zone was higher than that in the constant speedsection

1e difference between the experimental and theoreticalresults of concrete conveying was positively related to theconcrete throughput given the same flow rate of compressedair When the concrete throughput was small the experi-mental results and theoretical results were similar indicatingthat α was closer to 1 (Figure 10) With an increase ofconcrete throughput the difference of experimental andtheoretical results gradually increased 1e difference is thekey factor influencing the prediction of concrete conveying

Next the value of the transducer was fixed and theconcrete was input by the shotcrete machine at a constantfeeding rate Subsequently pressures at different points weretested by controlling the input of compressed air with the

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h

6m3h

Figure 8 Variation trend of concrete pressure

Stea

dy-s

tate

pre

ssur

e dro

p pe

run

it le

ngth

(Pa

m)

Concrete throughput4m3h5m3h6m3h

0

500

1000

1500

2000

2500

3000

38 42 46 50 54 58 62 66 7034Air flow rate (m3min)

Figure 7 Variations of pressure drop in the constant speed sectionwith air flow

Advances in Civil Engineering 7

regulating valve 1ere was a large difference between theexperimental results and theoretical results With an in-crease of air flow rate such differences decreased gradually1is difference was also a key factor that influenced theprediction of concrete conveying

Figures 10 and 11 show that the value of α had a directrelationship with concrete throughput and input of com-pressed air Tripathi et al tested materials of different grainsizes [29] and α can be defined as

α a + b middot eminus cmiddotμ

( 1113857 (19)

where μ mcmf is the ratio of concrete mass and air massExperimental data from Figures 11 and 12 were brought

into equation (19) yielding the following

α 12 + 011eminus 09μ

1113872 1113873 (20)

During the accelerated pressure drop experiment theconveying of concrete particles was accelerated at a specificspeed from one point and finally reached the movementtrend at a constant speed [30ndash32] 1e momentum equationwas used to calculate the pressure drop during this process

ΔPacc ΔPmom _ms middot Δuc

A

_ms middot ucss minus uc( 1113857

A (21)

Pressure drop is at equilibrium in the constant speedsection 1erefore the total accelerated pressure drop can begained from equations (18) (19) and (21) 1e totalaccelerated pressure drop was expressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961ΔPss +_ms middot ucss minus uc( 1113857

A

(22)

Also equations (1) and (2) were brought into equation(22) and thus the total accelerated pressure drop wasexpressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961 fDρfu2

f2D

L + ΔPc1113888 1113889

+_ms middot ucss minus uc( 1113857

A

(23)

To verify the accuracy of equation (20) the feedingrate of concrete was kept constant in the experiment 1econcrete-air ratio was changed by altering the air flow rateto analyze the pressure at different positions along theline Comparison between theoretical and experimental

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

65m3h

Figure 10 Comparison of theoretical and experimental pressuresafter adding α

Air flow

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

7m3min65m3min6m3min

55m3min

Figure 11 Comparison of pressure drop in the accelerate zone

ndash22

Air flowTheoretical trendExperimental trendError range

04

05

06

07

08

09

10

PP 0

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

Figure 9 Normalization trend under different wind speeds

8 Advances in Civil Engineering

pressures is shown in Figure 12 1e curve equationgained from the theoretical formula was similar to theexperimental results showing a maximum error of lessthan 10 1is verified the universality of equation (20)In this experiment pipe diameters of 20 inches and 25inches of the concrete line were applied Pressures atdifferent positions of the concrete line were tested by apressure transmitter (Figure 12) 1e maximum error wasless than 5 verifying the feasibility of equation (20)

5 Conclusions

In order to obtain the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying the concreteconveying pipeline was arranged to conduct the relatedconcrete conveying experiment 1e concrete was made upaccording to the common concrete ratio in the coal mineEach point pressure on the pipeline during the progress ofconveying was tested by the pressure transmitter set up onthe pipeline Also the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying was analyzed withmeasured pressure

1e results show that the pipeline pressure droppedrapidly at the beginning of the conveying and at the end ofthe bending pipe and the trend of the dropping linearly wasshowed gradually 1e accelerated pressure drop was ana-lyzed by combining experimental and momentum equationsduring concrete conveying 1e accelerated pressure dropwas analyzed which was mainly caused by accelerationfriction and the collision of concretes Also the friction andthe collision of concretes also exist in the zone of stableconvey

1e pressure drop curve was drawn according to thepressure at each point in the concrete conveying processAlso the mathematical model of pressure drop in theconcrete conveying process was set up To prevent random

interference factor from the friction and the collision andimproving the calculation accuracy the correction factor αwas introduced

Finally the measured pressures under different concretethroughputs and flow rates of compressed air were com-pared with the results from the mathematical model whichverified the accuracy of the mathematical model Also themain factors of pressure drop in the accelerate zone wereobtained as the ratio of the concrete mass and the com-pressed mass the initial velocity of the concrete the optimalfinal required velocity the feed speed of concrete and crosssection area of the conveying pipeline

Data Availability

1e data used to support the findings of this study areavailable from the corresponding author upon request

Additional Points

Innovations and highlights (1) Damage to the pressuretransmitter by concrete can be prevented by installing astrainer before the pressure transmitter (2) Variation laws ofpressure before and after the installation of a pressuretransmitter were studied by supplying air only (3) A sta-tistical analysis of the pressures at different positions alongthe concrete conveying line under different input quantitiesof concrete and compressed air was performed Based onthis the law of pressure drop during the conveying ofconcrete was discussed (4) 1e pressure drop in the lineduring the conveying of concrete was predicted

Conflicts of Interest

1e authors declare that they have no conflicts of interest

References

[1] L Chen G LiuW Cheng and G Pan ldquoPipe flow of pumpingwet shotcrete based on lubrication layerrdquo SpringerPlus vol 5no 1 p 945 2016

[2] Y Cai Y Jiang I Djamaluddin T Iura and T Esaki ldquoAnanalytical model considering interaction behavior of groutedrock bolts for convergence-confinement method in tunnelingdesignrdquo International Journal of Rock Mechanics and MiningSciences vol 76 pp 112ndash126 2015

[3] L Chen P Li G Liu W Cheng and Z Liu ldquoDevelopment ofcement dust suppression technology during shotcrete in mineof China-a reviewrdquo Journal of Loss Prevention in the ProcessIndustries vol 55 pp 232ndash242 2018

[4] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[5] Q Liu W Nie Y Hua H Peng and Z Liu ldquo1e effects of theinstallation position of a multi-radial swirling air-curtaingenerator on dust diffusion and pollution rules in a fully-mechanized excavation face a case studyrdquo Powder Technol-ogy vol 329 pp 371ndash385 2018

[6] R Naveh N M Tripathi and H Kalman ldquoExperimentalpressure drop analysis for horizontal dilute phase particle-fluid flowsrdquo Powder Technology vol 321 pp 353ndash368 2017

Pipe diameter

3

2inch25inch

Theoretical trendExperimental trend

5

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

Figure 12 Pressure drop at different specifications of concretelines

Advances in Civil Engineering 9

[7] O G Brown ldquo1e history of the Darcy-Weisbach equationfor pipe flow resistancerdquo in Proceedings of the Environmentaland Water Resources History pp 34ndash43 Washington DCUSA November 2003

[8] O Molerus ldquoOverview pneumatic transport of solidsrdquoPowder Technology vol 88 no 3 pp 309ndash321 1996

[9] Q LiuW Nie Y Hua H Peng C Liu and CWei ldquoResearchon tunnel ventilation systems dust diffusion and pollutionbehaviour by air curtains based on CFD technology and fieldmeasurementrdquo Building and Environment vol 147pp 444ndash460 2019

[10] Y-Q Zhang J-L Zhu X-H Wang X-W ZhangS-X Zhou and P Liang ldquoSimulation of large coal particlespyrolysis by circulating ash heat carrier toward the axialdimension of the moving bedrdquo Fuel Processing Technologyvol 154 pp 227ndash234 2016

[11] Y Tomita H Tashiro K Deguchi and T Jotaki ldquoSuddenexpansion of gas-solid two-phase flow in a piperdquo Physics ofFluids vol 23 no 4 pp 663ndash666 1980

[12] P Li Z Zhou L Chen G Liu and W Xiao ldquoResearch ondust suppression technology of shotcrete based on new sprayequipment and process optimizationrdquo Advances in CivilEngineering vol 2019 Article ID 4831215 11 pages 2019

[13] B Kong E Wang and Z Li ldquo1e effect of high temperatureenvironment on rock propertiesmdashan example of electro-magnetic radiation characterizationrdquo Environmental Scienceand Pollution Research vol 25 no 29 pp 1ndash11 2018

[14] A Shimizu R Echigo S Hasegawa and M Hishida ldquoEx-perimental study on the pressure drop and the entry length ofthe gas-solid suspension flow in a circular tuberdquo InternationalJournal of Multiphase Flow vol 4 no 1 pp 53ndash64 1978

[15] N Guanhua D Kai L Shang and S Qian ldquoGas desorptioncharacteristics effected by the pulsating hydraulic fracturingin coalrdquo Fuel vol 236 pp 190ndash200 2019

[16] G Zhou Y Ma T Fan and G Wang ldquoPreparation andcharacteristics of a multifunctional dust suppressant withagglomeration and wettability performance used in coalminerdquo Chemical Engineering Research and Design vol 132pp 729ndash742 2018

[17] R D Marcus J D Hilbert Jr and G E Klinzing ldquoFlowthrough bends and acceleration zones in pneumatic con-veying systemsrdquo Bulk Solids Handling vol 5 no 4 pp 121ndash126 1985

[18] T Fan G Zhou and J Wang ldquoPreparation and character-ization of a wetting-agglomeration-based hybrid coal dustsuppressantrdquo Process Safety and Environmental Protectionvol 113 pp 282ndash291 2018

[19] R A Duckworth Empirical Correlations Fore Dilute PhaseDepartment of Chemical Engineering 1e University ofQueensland Brisbane Australia Lecture notes CSIROMineral engineering 1969

[20] Y Tomita and H Tashiro ldquoLoss coefficient for abrupt en-largement in pneumatic transport of solids in pipesrdquo BulkSolid Handling vol 8 pp 129ndash131 1988

[21] J A Ottjes ldquoDigital simulation of pneumatic particletransportrdquo Chemical Engineering Science vol 33 no 6pp 783ndash786 1978

[22] H V Nguyen R Yokota G Stenchikov et al ldquoA paralleldirect numerical simulation of dust particles in a turbulentflowrdquo in Proceedings of the EGU General Assembly ConferenceAbstracts Vienna Austria April 2012

[23] N Huber and M Sommerfeld ldquoModelling and numericalcalculation of dilute-phase pneumatic conveying in pipesystemsrdquo Powder Technology vol 99 no 1 pp 90ndash101 1998

[24] K J Hanley E P Byrne and K Cronin ldquoProbabilisticanalysis of particle impact at a pipe bend in pneumaticconveyingrdquo Powder Technology vol 233 pp 176ndash185 2013

[25] G E Klinzing and O M Basha ldquoA correlation for particlevelocities in pneumatic conveyingrdquo Powder Technologyvol 310 pp 201ndash204 2017

[26] H G Merkus and G M H Meesters ldquoProduction handlingand characterization of particulate materialsrdquo Particle Tech-nology vol 11 no 4 pp 619ndash629 2016

[27] G Liu W Cheng and L Chen ldquoInvestigating and optimizingthe mix proportion of pumping wet-mix shotcrete withpolypropylene fiberrdquo Construction and Building Materialsvol 150 pp 14ndash23 2017

[28] W Wei G Qingliang W Yuxin Y Hairui Z Jiansheng andL Junfu ldquoExperimental study on the solid velocity in hori-zontal dilute phase pneumatic conveying of fine powdersrdquoPowder Technology vol 212 no 3 pp 403ndash409 2011

[29] N M Tripathi A Levy and H Kalman ldquoAccelerationpressure drop analysis in horizontal dilute phase pneumaticconveying systemrdquo Powder Technology vol 327 pp 43ndash562018

[30] L Chen G Ma G Liu and Z Liu ldquoEffect of pumping andspraying processes on the rheological properties and aircontent of wet-mix shotcrete with various admixturesrdquoConstruction and Building Materials vol 225 pp 311ndash3232019

[31] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[32] B Kong E Wang W Lu and Z Li ldquoApplication of elec-tromagnetic radiation detection in high-temperature anom-alous areas experiencing coalfield firesrdquo Energy vol 189Article ID 116144 2019

10 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

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Submit your manuscripts atwwwhindawicom

(2) In Figure 3(b) a strainer was placed on the mountingbase of the pressure transmitter Later the pressuretransmitter was installed to keep the bottom of thepressure transmitter 2mm away from the strainerCompressed air was supplied and pressures along theconcrete line were recorded by the pressure transmitter

Pressures under the above two conditions aresummarized in Figure 5 During this process thepressures at the different positions that were measuredby the two methods had a fixed difference of ΔP0 Whenthe pressure in the concrete conveying was measured bythe method in Figure 3(b) the pressure in the concreteline was equal to the sum of the measured pressure P0and ΔP0 In other words pressure changes after theaddition of a strainer could be used to reflect thepressure changes in the concrete lines throughoutconveying

1e acceleration pressure drop in the horizontal sectionof the concrete conveying was mainly caused by the meanpressure difference measured by the pressure transmitter1e measured acceleration pressure drop between any twopoints in the analysis region was discussed Howeverwhether concrete was in the initial section or had passed thebent line was neglected thus it was believed that the mo-mentum and energy changes were the same given the samevelocity changes

During the experiment pressure drop in the acceleratezone occurred as shown in Figure 6 1e pressure dropcurve shows that the pressure drop in the accelerate zonereached a relatively stable trend 1e pressure curveduring this process was fitted and a straight line repre-senting the steady-state pressure drop was deduced basedon the final process of the stable pressure drop Based onthis deduced straight line the pressure at zero speed couldbe determined

In Figure 6 ΔPacctotal is the total pressure drop in theaccelerate zone and ΔPacc is the acceleration pressure dropof concrete

According to reverse deduction from the stable value ofthe above curves energy loss under steady state can beobtained from the index trend and linear pressure gradienttrend of floating points leading to the acceleration ofpressure drop and thus obtaining the actual pressure droptrend An exponential linear equation was fitted by thepressure fitting curve in Figure 6

P0 p1 middot eminus xp2 + p3 middot x + p4 (3)

Here x is the length of the test section and p1 p2 p3 andp4 are constants 1e numerical value in Figure 6 wasbrought into equation (3) thus obtaining the followingequation

P0 11 middot eminus 036x

minus 45x + 307 (4)

1is pressure-distance relation equation covers twoparts (1) p1 middot eminus xp2 is the exponential function that reflectsthe pressure drop caused by the acceleration in the concreteline (2) p3 middot x + p4 is the linear function that reflects the

pressure drop caused by concrete collision and friction in theline Under this circumstance the pressure drop is dis-tributed uniformly Based on the above curves we can obtainthe following results

(a) Steady pressure drop in the concrete line(b) Accelerated pressure drop in the concrete line(c) 1e pressure at the beginning of acceleration is

difficult to measure Under this circumstance thepressure at the beginning of acceleration can bededuced by the equation 1us the pressure dropfrom zero to a steady speed could be calculated

(d) Length of the accelerate zone (part 1 in the equationis approaching zero)

To predict the length of the accelerate zone duringconcrete conveying Wei et al introduced the Archimedesnumber [28] 1e Archimedes number mainly reflects theratio between buoyancy and viscosity force and can beexpressed as

∆P

With strainerWithout strainer

260

270

280

290

300

310

320

330

340

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

Figure 5 Effects of the strainer in the pressure transmitter on thegas-phase pressure drop

Steady-statepressure drop

trendPressure point

Actual pressuredrop trend

Accelerate zone

Accelerate length

Steady-statezone

∆Pacc

∆Pacc total

∆Pss

260

270

280

290

300

310

320Pr

essu

re (k

Pa)

12106 8 14 162 4 18 200Distance (m)

Figure 6 Trend of pressure drop during concrete conveying

Advances in Civil Engineering 5

Ar ρc minus ρf( 1113857g middot d3

v2 middot ρf (5)

where Ar is the Archimedes number ρc is the density ofconcrete ρf is the density of air v is the kinematic viscosityand d is the mean diameter of concrete particles

In the present study the conveying speed of theconcrete particles was measured with a high-speedcamera Pressure changes in the concrete line weremeasured by the pressure transmitter 1e length of theaccelerate zone of concrete was expressed by particlespeed and pressure changes Moreover the relation be-tween the Archimedes number and length of the accel-erate zone was expressed as

Lacc 16Ar01 (6)

During the present experiment the total pressure dropin the accelerate zone was expressed as the sum of steady-state pressure drop and accelerated pressure drop (equation(7))1e accelerated pressure drop (ΔPacc) is the momentumequation of concrete and can be expressed as equation (8)

ΔPacctotal ΔPss + ΔPacc (7)

ΔPacc ΔPmom _msΔuc

A

_ms ucss minus 0( 1113857

A (8)

where ΔPacctotal is the total pressure drop of the acceleratezone ΔPacc is the accelerated pressure drop of concrete ΔPssis the constant pressure drop of concrete and _ms is the massvelocity of concrete particle flow

1e total pressure drop in equation (7)was used to calculatethe derivation of displacement and can be expressed as

dPacctotal

dxdPss

dx+dPacc

dx (9)

To analyze the steady-state speed and transient speedduring concrete conveying an equation was constructed inthe present experiment with reference to the study by Weiet al [28]

ucss

uf 1 minus 0072 Ar middot

ρc minus ρfv2 middot ρf

1113890 1113891

0091

(10)

uc

ucss 1 minus e

minus 48xLacc (11)

where ucss is the steady speed of concrete uc is the initialvelocity of concrete and uf is the air velocity 1e derivativeof distance was calculated based on equation (10) and wasbrought into equation (11)

dPacctotal

dxdPss

dx+

_ms

A

duc

dx (12)

1e value of uc in equation (8) was brought into equation(12) to obtain

dPacctotal

dxdPss

dx+

_ms middot ucss

A

duc

dx1 minus e

minus 48xLacc1113872 1113873 (13)

Based on the integration of the displacement x throughequation (13) the following was obtained

1113946Lacc

0

dPacctotal

dx1113888 1113889dx 1113946

Lacc

0

dPss

dx1113888 1113889dx minus 1113946

Lacc

0

_ms middot ucss

A

48Lacc

1 minus eminus 48xLacc1113872 1113873dx

(14)

1erefore

Ptotal _ms

Aucss middot e

minus 48Lacc( )x+ p3 middot x + p4 (15)

By comparing equations (3) and (15) the following wasobtained

p1 _ms

Aucss

p2 minus48Lacc

x

(16)

1us the accelerated pressure drop of concrete can beexpressed as

ΔPacc _ms

Aucss middot e

minus 48Lacc( )x

_ms

Aucss middot e

minus 4816Ar01( )x

_ms

Aucss

middot eminus 4816 ρcminus ρf( )gmiddotd3( ) v2 middotρf( )( )

01( 1113857x

(17)

To protect the accuracy of the conclusions the concreteflow trend in the constant speed section was verified bychanging the supply quantity of concrete and air input 1estarting point of the constant speed section was set at 15mafter the bent line In the experiment the concrete supplywas controlled by the rotating speed of the motor of thetransducer During this process the relationship between thepressure drop during concrete conveying and concretesupply was found as shown in Figure 71e figure shows theeffects of air flow and concrete supply quantity on pressuredrop during the conveying of concrete

However equation (7) focused on testing the physicalproperty of the accelerated pressure drop which is the re-lationship between the momentum equation and pneumatictransmission during the conveying of concrete To accuratelypredict the relationship of accelerated pressure drop in theconveying of concrete the correction factor αwas introduced toincrease the prediction accuracy 1erefore the prediction ofthe total pressure drop in the acceleration zonewas calculated as

ΔPacctotal αΔPss + ΔPacc (18)

4 Results and Discussions

It is very simple to predict the pressure drop during concreteconveying by experiments First it must be determined thatthe pressure drop during concrete conveying is caused byaccelerated conveying friction and the collision of con-cretes 1e pressure drop caused by the acceleration of

6 Advances in Civil Engineering

concrete is also called the accelerated pressure drop and itonly exists in the accelerate zone 1e pressure dropcaused by friction and collision is called the uniformpressure drop and it exists throughout the conveying ofconcrete 1erefore the pressure drop caused by accel-eration can be calculated by the accelerated pressure dropminus the uniform pressure In the calculation of pressuredrop during concrete conveying the sum of steady-statepressure drop and accelerated pressure drop is the totalpressure drop in the accelerate zone 1is relationship isbased on the hypothesis that the steady-state pressuredrop in the accelerate zone and constant speed section arethe same

When predicting the pressure drop during concreteconveying the accelerated pressure drop can be predictedby equation (8) Hence the steady-state speed in theconveying of concrete must be known which can be cal-culated by equations (10) and (11) During the presentexperiment the rotating speed of the motor was changed bythe transducer thus changing the mass flow rate duringconcrete conveying Simultaneously the pressures at dif-ferent positions in the accelerate zone and constant speedzone could be measured

1e experimental pressure drop trend of concrete underdifferent mass flow rates is shown in Figure 8 which iscomparing the curves drawn based on equation (17) Fig-ure 8 shows that the increasing trend of the curves underdifferent supply quantities of concrete is the same Based onthe comparison of the curves drawn in accordance withFigure 8 the theoretical trend might overlap with the actualcurve measured in the experiment If these two curvesoverlap then the actual pressure drop during concreteconveying is similar to the predicted pressure drop provingthe accuracy of the prediction If the actual pressure dropdoes not overlap with the predicted pressure drop thesteady-state pressure drop in the accelerate zone is differentfrom that in the constant speed zone

1e effects of concrete pressure (p0) at the beginningposition on the pressure drop trend along the concreteconveying are shown in Figure 9 Normalization of pressureduring concrete conveying based on p0 can decrease theinfluence of the air flow rate on the pressure measurementand the maximum error can be controlled within 2

During multiple experimental processes the value of αwas calculated by changing the air flow rate and feeding rateof concrete under different motor speeds

Accelerated pressure drop and uniform pressure dropduring the concrete conveying were predicted based on thevalue of α If α 1 the pressure drop caused by concretecollision and friction was the same in the constant speedsection If αlt 1 the pressure drop was relatively small be-cause of the low conveying speed of concrete In contrastαgt 1 indicates a high pressure drop because of the highconveying speed of concrete In the constant speed section ofconcrete particle collision was weak However particlecollision frequency was high and particle collision wasstrong in the accelerate zone resulting in the high energyloss of concrete particles 1erefore the pressure drop in theaccelerate zone was higher than that in the constant speedsection

1e difference between the experimental and theoreticalresults of concrete conveying was positively related to theconcrete throughput given the same flow rate of compressedair When the concrete throughput was small the experi-mental results and theoretical results were similar indicatingthat α was closer to 1 (Figure 10) With an increase ofconcrete throughput the difference of experimental andtheoretical results gradually increased 1e difference is thekey factor influencing the prediction of concrete conveying

Next the value of the transducer was fixed and theconcrete was input by the shotcrete machine at a constantfeeding rate Subsequently pressures at different points weretested by controlling the input of compressed air with the

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h

6m3h

Figure 8 Variation trend of concrete pressure

Stea

dy-s

tate

pre

ssur

e dro

p pe

run

it le

ngth

(Pa

m)

Concrete throughput4m3h5m3h6m3h

0

500

1000

1500

2000

2500

3000

38 42 46 50 54 58 62 66 7034Air flow rate (m3min)

Figure 7 Variations of pressure drop in the constant speed sectionwith air flow

Advances in Civil Engineering 7

regulating valve 1ere was a large difference between theexperimental results and theoretical results With an in-crease of air flow rate such differences decreased gradually1is difference was also a key factor that influenced theprediction of concrete conveying

Figures 10 and 11 show that the value of α had a directrelationship with concrete throughput and input of com-pressed air Tripathi et al tested materials of different grainsizes [29] and α can be defined as

α a + b middot eminus cmiddotμ

( 1113857 (19)

where μ mcmf is the ratio of concrete mass and air massExperimental data from Figures 11 and 12 were brought

into equation (19) yielding the following

α 12 + 011eminus 09μ

1113872 1113873 (20)

During the accelerated pressure drop experiment theconveying of concrete particles was accelerated at a specificspeed from one point and finally reached the movementtrend at a constant speed [30ndash32] 1e momentum equationwas used to calculate the pressure drop during this process

ΔPacc ΔPmom _ms middot Δuc

A

_ms middot ucss minus uc( 1113857

A (21)

Pressure drop is at equilibrium in the constant speedsection 1erefore the total accelerated pressure drop can begained from equations (18) (19) and (21) 1e totalaccelerated pressure drop was expressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961ΔPss +_ms middot ucss minus uc( 1113857

A

(22)

Also equations (1) and (2) were brought into equation(22) and thus the total accelerated pressure drop wasexpressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961 fDρfu2

f2D

L + ΔPc1113888 1113889

+_ms middot ucss minus uc( 1113857

A

(23)

To verify the accuracy of equation (20) the feedingrate of concrete was kept constant in the experiment 1econcrete-air ratio was changed by altering the air flow rateto analyze the pressure at different positions along theline Comparison between theoretical and experimental

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

65m3h

Figure 10 Comparison of theoretical and experimental pressuresafter adding α

Air flow

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

7m3min65m3min6m3min

55m3min

Figure 11 Comparison of pressure drop in the accelerate zone

ndash22

Air flowTheoretical trendExperimental trendError range

04

05

06

07

08

09

10

PP 0

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

Figure 9 Normalization trend under different wind speeds

8 Advances in Civil Engineering

pressures is shown in Figure 12 1e curve equationgained from the theoretical formula was similar to theexperimental results showing a maximum error of lessthan 10 1is verified the universality of equation (20)In this experiment pipe diameters of 20 inches and 25inches of the concrete line were applied Pressures atdifferent positions of the concrete line were tested by apressure transmitter (Figure 12) 1e maximum error wasless than 5 verifying the feasibility of equation (20)

5 Conclusions

In order to obtain the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying the concreteconveying pipeline was arranged to conduct the relatedconcrete conveying experiment 1e concrete was made upaccording to the common concrete ratio in the coal mineEach point pressure on the pipeline during the progress ofconveying was tested by the pressure transmitter set up onthe pipeline Also the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying was analyzed withmeasured pressure

1e results show that the pipeline pressure droppedrapidly at the beginning of the conveying and at the end ofthe bending pipe and the trend of the dropping linearly wasshowed gradually 1e accelerated pressure drop was ana-lyzed by combining experimental and momentum equationsduring concrete conveying 1e accelerated pressure dropwas analyzed which was mainly caused by accelerationfriction and the collision of concretes Also the friction andthe collision of concretes also exist in the zone of stableconvey

1e pressure drop curve was drawn according to thepressure at each point in the concrete conveying processAlso the mathematical model of pressure drop in theconcrete conveying process was set up To prevent random

interference factor from the friction and the collision andimproving the calculation accuracy the correction factor αwas introduced

Finally the measured pressures under different concretethroughputs and flow rates of compressed air were com-pared with the results from the mathematical model whichverified the accuracy of the mathematical model Also themain factors of pressure drop in the accelerate zone wereobtained as the ratio of the concrete mass and the com-pressed mass the initial velocity of the concrete the optimalfinal required velocity the feed speed of concrete and crosssection area of the conveying pipeline

Data Availability

1e data used to support the findings of this study areavailable from the corresponding author upon request

Additional Points

Innovations and highlights (1) Damage to the pressuretransmitter by concrete can be prevented by installing astrainer before the pressure transmitter (2) Variation laws ofpressure before and after the installation of a pressuretransmitter were studied by supplying air only (3) A sta-tistical analysis of the pressures at different positions alongthe concrete conveying line under different input quantitiesof concrete and compressed air was performed Based onthis the law of pressure drop during the conveying ofconcrete was discussed (4) 1e pressure drop in the lineduring the conveying of concrete was predicted

Conflicts of Interest

1e authors declare that they have no conflicts of interest

References

[1] L Chen G LiuW Cheng and G Pan ldquoPipe flow of pumpingwet shotcrete based on lubrication layerrdquo SpringerPlus vol 5no 1 p 945 2016

[2] Y Cai Y Jiang I Djamaluddin T Iura and T Esaki ldquoAnanalytical model considering interaction behavior of groutedrock bolts for convergence-confinement method in tunnelingdesignrdquo International Journal of Rock Mechanics and MiningSciences vol 76 pp 112ndash126 2015

[3] L Chen P Li G Liu W Cheng and Z Liu ldquoDevelopment ofcement dust suppression technology during shotcrete in mineof China-a reviewrdquo Journal of Loss Prevention in the ProcessIndustries vol 55 pp 232ndash242 2018

[4] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[5] Q Liu W Nie Y Hua H Peng and Z Liu ldquo1e effects of theinstallation position of a multi-radial swirling air-curtaingenerator on dust diffusion and pollution rules in a fully-mechanized excavation face a case studyrdquo Powder Technol-ogy vol 329 pp 371ndash385 2018

[6] R Naveh N M Tripathi and H Kalman ldquoExperimentalpressure drop analysis for horizontal dilute phase particle-fluid flowsrdquo Powder Technology vol 321 pp 353ndash368 2017

Pipe diameter

3

2inch25inch

Theoretical trendExperimental trend

5

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

Figure 12 Pressure drop at different specifications of concretelines

Advances in Civil Engineering 9

[7] O G Brown ldquo1e history of the Darcy-Weisbach equationfor pipe flow resistancerdquo in Proceedings of the Environmentaland Water Resources History pp 34ndash43 Washington DCUSA November 2003

[8] O Molerus ldquoOverview pneumatic transport of solidsrdquoPowder Technology vol 88 no 3 pp 309ndash321 1996

[9] Q LiuW Nie Y Hua H Peng C Liu and CWei ldquoResearchon tunnel ventilation systems dust diffusion and pollutionbehaviour by air curtains based on CFD technology and fieldmeasurementrdquo Building and Environment vol 147pp 444ndash460 2019

[10] Y-Q Zhang J-L Zhu X-H Wang X-W ZhangS-X Zhou and P Liang ldquoSimulation of large coal particlespyrolysis by circulating ash heat carrier toward the axialdimension of the moving bedrdquo Fuel Processing Technologyvol 154 pp 227ndash234 2016

[11] Y Tomita H Tashiro K Deguchi and T Jotaki ldquoSuddenexpansion of gas-solid two-phase flow in a piperdquo Physics ofFluids vol 23 no 4 pp 663ndash666 1980

[12] P Li Z Zhou L Chen G Liu and W Xiao ldquoResearch ondust suppression technology of shotcrete based on new sprayequipment and process optimizationrdquo Advances in CivilEngineering vol 2019 Article ID 4831215 11 pages 2019

[13] B Kong E Wang and Z Li ldquo1e effect of high temperatureenvironment on rock propertiesmdashan example of electro-magnetic radiation characterizationrdquo Environmental Scienceand Pollution Research vol 25 no 29 pp 1ndash11 2018

[14] A Shimizu R Echigo S Hasegawa and M Hishida ldquoEx-perimental study on the pressure drop and the entry length ofthe gas-solid suspension flow in a circular tuberdquo InternationalJournal of Multiphase Flow vol 4 no 1 pp 53ndash64 1978

[15] N Guanhua D Kai L Shang and S Qian ldquoGas desorptioncharacteristics effected by the pulsating hydraulic fracturingin coalrdquo Fuel vol 236 pp 190ndash200 2019

[16] G Zhou Y Ma T Fan and G Wang ldquoPreparation andcharacteristics of a multifunctional dust suppressant withagglomeration and wettability performance used in coalminerdquo Chemical Engineering Research and Design vol 132pp 729ndash742 2018

[17] R D Marcus J D Hilbert Jr and G E Klinzing ldquoFlowthrough bends and acceleration zones in pneumatic con-veying systemsrdquo Bulk Solids Handling vol 5 no 4 pp 121ndash126 1985

[18] T Fan G Zhou and J Wang ldquoPreparation and character-ization of a wetting-agglomeration-based hybrid coal dustsuppressantrdquo Process Safety and Environmental Protectionvol 113 pp 282ndash291 2018

[19] R A Duckworth Empirical Correlations Fore Dilute PhaseDepartment of Chemical Engineering 1e University ofQueensland Brisbane Australia Lecture notes CSIROMineral engineering 1969

[20] Y Tomita and H Tashiro ldquoLoss coefficient for abrupt en-largement in pneumatic transport of solids in pipesrdquo BulkSolid Handling vol 8 pp 129ndash131 1988

[21] J A Ottjes ldquoDigital simulation of pneumatic particletransportrdquo Chemical Engineering Science vol 33 no 6pp 783ndash786 1978

[22] H V Nguyen R Yokota G Stenchikov et al ldquoA paralleldirect numerical simulation of dust particles in a turbulentflowrdquo in Proceedings of the EGU General Assembly ConferenceAbstracts Vienna Austria April 2012

[23] N Huber and M Sommerfeld ldquoModelling and numericalcalculation of dilute-phase pneumatic conveying in pipesystemsrdquo Powder Technology vol 99 no 1 pp 90ndash101 1998

[24] K J Hanley E P Byrne and K Cronin ldquoProbabilisticanalysis of particle impact at a pipe bend in pneumaticconveyingrdquo Powder Technology vol 233 pp 176ndash185 2013

[25] G E Klinzing and O M Basha ldquoA correlation for particlevelocities in pneumatic conveyingrdquo Powder Technologyvol 310 pp 201ndash204 2017

[26] H G Merkus and G M H Meesters ldquoProduction handlingand characterization of particulate materialsrdquo Particle Tech-nology vol 11 no 4 pp 619ndash629 2016

[27] G Liu W Cheng and L Chen ldquoInvestigating and optimizingthe mix proportion of pumping wet-mix shotcrete withpolypropylene fiberrdquo Construction and Building Materialsvol 150 pp 14ndash23 2017

[28] W Wei G Qingliang W Yuxin Y Hairui Z Jiansheng andL Junfu ldquoExperimental study on the solid velocity in hori-zontal dilute phase pneumatic conveying of fine powdersrdquoPowder Technology vol 212 no 3 pp 403ndash409 2011

[29] N M Tripathi A Levy and H Kalman ldquoAccelerationpressure drop analysis in horizontal dilute phase pneumaticconveying systemrdquo Powder Technology vol 327 pp 43ndash562018

[30] L Chen G Ma G Liu and Z Liu ldquoEffect of pumping andspraying processes on the rheological properties and aircontent of wet-mix shotcrete with various admixturesrdquoConstruction and Building Materials vol 225 pp 311ndash3232019

[31] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[32] B Kong E Wang W Lu and Z Li ldquoApplication of elec-tromagnetic radiation detection in high-temperature anom-alous areas experiencing coalfield firesrdquo Energy vol 189Article ID 116144 2019

10 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

Ar ρc minus ρf( 1113857g middot d3

v2 middot ρf (5)

where Ar is the Archimedes number ρc is the density ofconcrete ρf is the density of air v is the kinematic viscosityand d is the mean diameter of concrete particles

In the present study the conveying speed of theconcrete particles was measured with a high-speedcamera Pressure changes in the concrete line weremeasured by the pressure transmitter 1e length of theaccelerate zone of concrete was expressed by particlespeed and pressure changes Moreover the relation be-tween the Archimedes number and length of the accel-erate zone was expressed as

Lacc 16Ar01 (6)

During the present experiment the total pressure dropin the accelerate zone was expressed as the sum of steady-state pressure drop and accelerated pressure drop (equation(7))1e accelerated pressure drop (ΔPacc) is the momentumequation of concrete and can be expressed as equation (8)

ΔPacctotal ΔPss + ΔPacc (7)

ΔPacc ΔPmom _msΔuc

A

_ms ucss minus 0( 1113857

A (8)

where ΔPacctotal is the total pressure drop of the acceleratezone ΔPacc is the accelerated pressure drop of concrete ΔPssis the constant pressure drop of concrete and _ms is the massvelocity of concrete particle flow

1e total pressure drop in equation (7)was used to calculatethe derivation of displacement and can be expressed as

dPacctotal

dxdPss

dx+dPacc

dx (9)

To analyze the steady-state speed and transient speedduring concrete conveying an equation was constructed inthe present experiment with reference to the study by Weiet al [28]

ucss

uf 1 minus 0072 Ar middot

ρc minus ρfv2 middot ρf

1113890 1113891

0091

(10)

uc

ucss 1 minus e

minus 48xLacc (11)

where ucss is the steady speed of concrete uc is the initialvelocity of concrete and uf is the air velocity 1e derivativeof distance was calculated based on equation (10) and wasbrought into equation (11)

dPacctotal

dxdPss

dx+

_ms

A

duc

dx (12)

1e value of uc in equation (8) was brought into equation(12) to obtain

dPacctotal

dxdPss

dx+

_ms middot ucss

A

duc

dx1 minus e

minus 48xLacc1113872 1113873 (13)

Based on the integration of the displacement x throughequation (13) the following was obtained

1113946Lacc

0

dPacctotal

dx1113888 1113889dx 1113946

Lacc

0

dPss

dx1113888 1113889dx minus 1113946

Lacc

0

_ms middot ucss

A

48Lacc

1 minus eminus 48xLacc1113872 1113873dx

(14)

1erefore

Ptotal _ms

Aucss middot e

minus 48Lacc( )x+ p3 middot x + p4 (15)

By comparing equations (3) and (15) the following wasobtained

p1 _ms

Aucss

p2 minus48Lacc

x

(16)

1us the accelerated pressure drop of concrete can beexpressed as

ΔPacc _ms

Aucss middot e

minus 48Lacc( )x

_ms

Aucss middot e

minus 4816Ar01( )x

_ms

Aucss

middot eminus 4816 ρcminus ρf( )gmiddotd3( ) v2 middotρf( )( )

01( 1113857x

(17)

To protect the accuracy of the conclusions the concreteflow trend in the constant speed section was verified bychanging the supply quantity of concrete and air input 1estarting point of the constant speed section was set at 15mafter the bent line In the experiment the concrete supplywas controlled by the rotating speed of the motor of thetransducer During this process the relationship between thepressure drop during concrete conveying and concretesupply was found as shown in Figure 71e figure shows theeffects of air flow and concrete supply quantity on pressuredrop during the conveying of concrete

However equation (7) focused on testing the physicalproperty of the accelerated pressure drop which is the re-lationship between the momentum equation and pneumatictransmission during the conveying of concrete To accuratelypredict the relationship of accelerated pressure drop in theconveying of concrete the correction factor αwas introduced toincrease the prediction accuracy 1erefore the prediction ofthe total pressure drop in the acceleration zonewas calculated as

ΔPacctotal αΔPss + ΔPacc (18)

4 Results and Discussions

It is very simple to predict the pressure drop during concreteconveying by experiments First it must be determined thatthe pressure drop during concrete conveying is caused byaccelerated conveying friction and the collision of con-cretes 1e pressure drop caused by the acceleration of

6 Advances in Civil Engineering

concrete is also called the accelerated pressure drop and itonly exists in the accelerate zone 1e pressure dropcaused by friction and collision is called the uniformpressure drop and it exists throughout the conveying ofconcrete 1erefore the pressure drop caused by accel-eration can be calculated by the accelerated pressure dropminus the uniform pressure In the calculation of pressuredrop during concrete conveying the sum of steady-statepressure drop and accelerated pressure drop is the totalpressure drop in the accelerate zone 1is relationship isbased on the hypothesis that the steady-state pressuredrop in the accelerate zone and constant speed section arethe same

When predicting the pressure drop during concreteconveying the accelerated pressure drop can be predictedby equation (8) Hence the steady-state speed in theconveying of concrete must be known which can be cal-culated by equations (10) and (11) During the presentexperiment the rotating speed of the motor was changed bythe transducer thus changing the mass flow rate duringconcrete conveying Simultaneously the pressures at dif-ferent positions in the accelerate zone and constant speedzone could be measured

1e experimental pressure drop trend of concrete underdifferent mass flow rates is shown in Figure 8 which iscomparing the curves drawn based on equation (17) Fig-ure 8 shows that the increasing trend of the curves underdifferent supply quantities of concrete is the same Based onthe comparison of the curves drawn in accordance withFigure 8 the theoretical trend might overlap with the actualcurve measured in the experiment If these two curvesoverlap then the actual pressure drop during concreteconveying is similar to the predicted pressure drop provingthe accuracy of the prediction If the actual pressure dropdoes not overlap with the predicted pressure drop thesteady-state pressure drop in the accelerate zone is differentfrom that in the constant speed zone

1e effects of concrete pressure (p0) at the beginningposition on the pressure drop trend along the concreteconveying are shown in Figure 9 Normalization of pressureduring concrete conveying based on p0 can decrease theinfluence of the air flow rate on the pressure measurementand the maximum error can be controlled within 2

During multiple experimental processes the value of αwas calculated by changing the air flow rate and feeding rateof concrete under different motor speeds

Accelerated pressure drop and uniform pressure dropduring the concrete conveying were predicted based on thevalue of α If α 1 the pressure drop caused by concretecollision and friction was the same in the constant speedsection If αlt 1 the pressure drop was relatively small be-cause of the low conveying speed of concrete In contrastαgt 1 indicates a high pressure drop because of the highconveying speed of concrete In the constant speed section ofconcrete particle collision was weak However particlecollision frequency was high and particle collision wasstrong in the accelerate zone resulting in the high energyloss of concrete particles 1erefore the pressure drop in theaccelerate zone was higher than that in the constant speedsection

1e difference between the experimental and theoreticalresults of concrete conveying was positively related to theconcrete throughput given the same flow rate of compressedair When the concrete throughput was small the experi-mental results and theoretical results were similar indicatingthat α was closer to 1 (Figure 10) With an increase ofconcrete throughput the difference of experimental andtheoretical results gradually increased 1e difference is thekey factor influencing the prediction of concrete conveying

Next the value of the transducer was fixed and theconcrete was input by the shotcrete machine at a constantfeeding rate Subsequently pressures at different points weretested by controlling the input of compressed air with the

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h

6m3h

Figure 8 Variation trend of concrete pressure

Stea

dy-s

tate

pre

ssur

e dro

p pe

run

it le

ngth

(Pa

m)

Concrete throughput4m3h5m3h6m3h

0

500

1000

1500

2000

2500

3000

38 42 46 50 54 58 62 66 7034Air flow rate (m3min)

Figure 7 Variations of pressure drop in the constant speed sectionwith air flow

Advances in Civil Engineering 7

regulating valve 1ere was a large difference between theexperimental results and theoretical results With an in-crease of air flow rate such differences decreased gradually1is difference was also a key factor that influenced theprediction of concrete conveying

Figures 10 and 11 show that the value of α had a directrelationship with concrete throughput and input of com-pressed air Tripathi et al tested materials of different grainsizes [29] and α can be defined as

α a + b middot eminus cmiddotμ

( 1113857 (19)

where μ mcmf is the ratio of concrete mass and air massExperimental data from Figures 11 and 12 were brought

into equation (19) yielding the following

α 12 + 011eminus 09μ

1113872 1113873 (20)

During the accelerated pressure drop experiment theconveying of concrete particles was accelerated at a specificspeed from one point and finally reached the movementtrend at a constant speed [30ndash32] 1e momentum equationwas used to calculate the pressure drop during this process

ΔPacc ΔPmom _ms middot Δuc

A

_ms middot ucss minus uc( 1113857

A (21)

Pressure drop is at equilibrium in the constant speedsection 1erefore the total accelerated pressure drop can begained from equations (18) (19) and (21) 1e totalaccelerated pressure drop was expressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961ΔPss +_ms middot ucss minus uc( 1113857

A

(22)

Also equations (1) and (2) were brought into equation(22) and thus the total accelerated pressure drop wasexpressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961 fDρfu2

f2D

L + ΔPc1113888 1113889

+_ms middot ucss minus uc( 1113857

A

(23)

To verify the accuracy of equation (20) the feedingrate of concrete was kept constant in the experiment 1econcrete-air ratio was changed by altering the air flow rateto analyze the pressure at different positions along theline Comparison between theoretical and experimental

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

65m3h

Figure 10 Comparison of theoretical and experimental pressuresafter adding α

Air flow

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

7m3min65m3min6m3min

55m3min

Figure 11 Comparison of pressure drop in the accelerate zone

ndash22

Air flowTheoretical trendExperimental trendError range

04

05

06

07

08

09

10

PP 0

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

Figure 9 Normalization trend under different wind speeds

8 Advances in Civil Engineering

pressures is shown in Figure 12 1e curve equationgained from the theoretical formula was similar to theexperimental results showing a maximum error of lessthan 10 1is verified the universality of equation (20)In this experiment pipe diameters of 20 inches and 25inches of the concrete line were applied Pressures atdifferent positions of the concrete line were tested by apressure transmitter (Figure 12) 1e maximum error wasless than 5 verifying the feasibility of equation (20)

5 Conclusions

In order to obtain the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying the concreteconveying pipeline was arranged to conduct the relatedconcrete conveying experiment 1e concrete was made upaccording to the common concrete ratio in the coal mineEach point pressure on the pipeline during the progress ofconveying was tested by the pressure transmitter set up onthe pipeline Also the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying was analyzed withmeasured pressure

1e results show that the pipeline pressure droppedrapidly at the beginning of the conveying and at the end ofthe bending pipe and the trend of the dropping linearly wasshowed gradually 1e accelerated pressure drop was ana-lyzed by combining experimental and momentum equationsduring concrete conveying 1e accelerated pressure dropwas analyzed which was mainly caused by accelerationfriction and the collision of concretes Also the friction andthe collision of concretes also exist in the zone of stableconvey

1e pressure drop curve was drawn according to thepressure at each point in the concrete conveying processAlso the mathematical model of pressure drop in theconcrete conveying process was set up To prevent random

interference factor from the friction and the collision andimproving the calculation accuracy the correction factor αwas introduced

Finally the measured pressures under different concretethroughputs and flow rates of compressed air were com-pared with the results from the mathematical model whichverified the accuracy of the mathematical model Also themain factors of pressure drop in the accelerate zone wereobtained as the ratio of the concrete mass and the com-pressed mass the initial velocity of the concrete the optimalfinal required velocity the feed speed of concrete and crosssection area of the conveying pipeline

Data Availability

1e data used to support the findings of this study areavailable from the corresponding author upon request

Additional Points

Innovations and highlights (1) Damage to the pressuretransmitter by concrete can be prevented by installing astrainer before the pressure transmitter (2) Variation laws ofpressure before and after the installation of a pressuretransmitter were studied by supplying air only (3) A sta-tistical analysis of the pressures at different positions alongthe concrete conveying line under different input quantitiesof concrete and compressed air was performed Based onthis the law of pressure drop during the conveying ofconcrete was discussed (4) 1e pressure drop in the lineduring the conveying of concrete was predicted

Conflicts of Interest

1e authors declare that they have no conflicts of interest

References

[1] L Chen G LiuW Cheng and G Pan ldquoPipe flow of pumpingwet shotcrete based on lubrication layerrdquo SpringerPlus vol 5no 1 p 945 2016

[2] Y Cai Y Jiang I Djamaluddin T Iura and T Esaki ldquoAnanalytical model considering interaction behavior of groutedrock bolts for convergence-confinement method in tunnelingdesignrdquo International Journal of Rock Mechanics and MiningSciences vol 76 pp 112ndash126 2015

[3] L Chen P Li G Liu W Cheng and Z Liu ldquoDevelopment ofcement dust suppression technology during shotcrete in mineof China-a reviewrdquo Journal of Loss Prevention in the ProcessIndustries vol 55 pp 232ndash242 2018

[4] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[5] Q Liu W Nie Y Hua H Peng and Z Liu ldquo1e effects of theinstallation position of a multi-radial swirling air-curtaingenerator on dust diffusion and pollution rules in a fully-mechanized excavation face a case studyrdquo Powder Technol-ogy vol 329 pp 371ndash385 2018

[6] R Naveh N M Tripathi and H Kalman ldquoExperimentalpressure drop analysis for horizontal dilute phase particle-fluid flowsrdquo Powder Technology vol 321 pp 353ndash368 2017

Pipe diameter

3

2inch25inch

Theoretical trendExperimental trend

5

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

Figure 12 Pressure drop at different specifications of concretelines

Advances in Civil Engineering 9

[7] O G Brown ldquo1e history of the Darcy-Weisbach equationfor pipe flow resistancerdquo in Proceedings of the Environmentaland Water Resources History pp 34ndash43 Washington DCUSA November 2003

[8] O Molerus ldquoOverview pneumatic transport of solidsrdquoPowder Technology vol 88 no 3 pp 309ndash321 1996

[9] Q LiuW Nie Y Hua H Peng C Liu and CWei ldquoResearchon tunnel ventilation systems dust diffusion and pollutionbehaviour by air curtains based on CFD technology and fieldmeasurementrdquo Building and Environment vol 147pp 444ndash460 2019

[10] Y-Q Zhang J-L Zhu X-H Wang X-W ZhangS-X Zhou and P Liang ldquoSimulation of large coal particlespyrolysis by circulating ash heat carrier toward the axialdimension of the moving bedrdquo Fuel Processing Technologyvol 154 pp 227ndash234 2016

[11] Y Tomita H Tashiro K Deguchi and T Jotaki ldquoSuddenexpansion of gas-solid two-phase flow in a piperdquo Physics ofFluids vol 23 no 4 pp 663ndash666 1980

[12] P Li Z Zhou L Chen G Liu and W Xiao ldquoResearch ondust suppression technology of shotcrete based on new sprayequipment and process optimizationrdquo Advances in CivilEngineering vol 2019 Article ID 4831215 11 pages 2019

[13] B Kong E Wang and Z Li ldquo1e effect of high temperatureenvironment on rock propertiesmdashan example of electro-magnetic radiation characterizationrdquo Environmental Scienceand Pollution Research vol 25 no 29 pp 1ndash11 2018

[14] A Shimizu R Echigo S Hasegawa and M Hishida ldquoEx-perimental study on the pressure drop and the entry length ofthe gas-solid suspension flow in a circular tuberdquo InternationalJournal of Multiphase Flow vol 4 no 1 pp 53ndash64 1978

[15] N Guanhua D Kai L Shang and S Qian ldquoGas desorptioncharacteristics effected by the pulsating hydraulic fracturingin coalrdquo Fuel vol 236 pp 190ndash200 2019

[16] G Zhou Y Ma T Fan and G Wang ldquoPreparation andcharacteristics of a multifunctional dust suppressant withagglomeration and wettability performance used in coalminerdquo Chemical Engineering Research and Design vol 132pp 729ndash742 2018

[17] R D Marcus J D Hilbert Jr and G E Klinzing ldquoFlowthrough bends and acceleration zones in pneumatic con-veying systemsrdquo Bulk Solids Handling vol 5 no 4 pp 121ndash126 1985

[18] T Fan G Zhou and J Wang ldquoPreparation and character-ization of a wetting-agglomeration-based hybrid coal dustsuppressantrdquo Process Safety and Environmental Protectionvol 113 pp 282ndash291 2018

[19] R A Duckworth Empirical Correlations Fore Dilute PhaseDepartment of Chemical Engineering 1e University ofQueensland Brisbane Australia Lecture notes CSIROMineral engineering 1969

[20] Y Tomita and H Tashiro ldquoLoss coefficient for abrupt en-largement in pneumatic transport of solids in pipesrdquo BulkSolid Handling vol 8 pp 129ndash131 1988

[21] J A Ottjes ldquoDigital simulation of pneumatic particletransportrdquo Chemical Engineering Science vol 33 no 6pp 783ndash786 1978

[22] H V Nguyen R Yokota G Stenchikov et al ldquoA paralleldirect numerical simulation of dust particles in a turbulentflowrdquo in Proceedings of the EGU General Assembly ConferenceAbstracts Vienna Austria April 2012

[23] N Huber and M Sommerfeld ldquoModelling and numericalcalculation of dilute-phase pneumatic conveying in pipesystemsrdquo Powder Technology vol 99 no 1 pp 90ndash101 1998

[24] K J Hanley E P Byrne and K Cronin ldquoProbabilisticanalysis of particle impact at a pipe bend in pneumaticconveyingrdquo Powder Technology vol 233 pp 176ndash185 2013

[25] G E Klinzing and O M Basha ldquoA correlation for particlevelocities in pneumatic conveyingrdquo Powder Technologyvol 310 pp 201ndash204 2017

[26] H G Merkus and G M H Meesters ldquoProduction handlingand characterization of particulate materialsrdquo Particle Tech-nology vol 11 no 4 pp 619ndash629 2016

[27] G Liu W Cheng and L Chen ldquoInvestigating and optimizingthe mix proportion of pumping wet-mix shotcrete withpolypropylene fiberrdquo Construction and Building Materialsvol 150 pp 14ndash23 2017

[28] W Wei G Qingliang W Yuxin Y Hairui Z Jiansheng andL Junfu ldquoExperimental study on the solid velocity in hori-zontal dilute phase pneumatic conveying of fine powdersrdquoPowder Technology vol 212 no 3 pp 403ndash409 2011

[29] N M Tripathi A Levy and H Kalman ldquoAccelerationpressure drop analysis in horizontal dilute phase pneumaticconveying systemrdquo Powder Technology vol 327 pp 43ndash562018

[30] L Chen G Ma G Liu and Z Liu ldquoEffect of pumping andspraying processes on the rheological properties and aircontent of wet-mix shotcrete with various admixturesrdquoConstruction and Building Materials vol 225 pp 311ndash3232019

[31] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[32] B Kong E Wang W Lu and Z Li ldquoApplication of elec-tromagnetic radiation detection in high-temperature anom-alous areas experiencing coalfield firesrdquo Energy vol 189Article ID 116144 2019

10 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

concrete is also called the accelerated pressure drop and itonly exists in the accelerate zone 1e pressure dropcaused by friction and collision is called the uniformpressure drop and it exists throughout the conveying ofconcrete 1erefore the pressure drop caused by accel-eration can be calculated by the accelerated pressure dropminus the uniform pressure In the calculation of pressuredrop during concrete conveying the sum of steady-statepressure drop and accelerated pressure drop is the totalpressure drop in the accelerate zone 1is relationship isbased on the hypothesis that the steady-state pressuredrop in the accelerate zone and constant speed section arethe same

When predicting the pressure drop during concreteconveying the accelerated pressure drop can be predictedby equation (8) Hence the steady-state speed in theconveying of concrete must be known which can be cal-culated by equations (10) and (11) During the presentexperiment the rotating speed of the motor was changed bythe transducer thus changing the mass flow rate duringconcrete conveying Simultaneously the pressures at dif-ferent positions in the accelerate zone and constant speedzone could be measured

1e experimental pressure drop trend of concrete underdifferent mass flow rates is shown in Figure 8 which iscomparing the curves drawn based on equation (17) Fig-ure 8 shows that the increasing trend of the curves underdifferent supply quantities of concrete is the same Based onthe comparison of the curves drawn in accordance withFigure 8 the theoretical trend might overlap with the actualcurve measured in the experiment If these two curvesoverlap then the actual pressure drop during concreteconveying is similar to the predicted pressure drop provingthe accuracy of the prediction If the actual pressure dropdoes not overlap with the predicted pressure drop thesteady-state pressure drop in the accelerate zone is differentfrom that in the constant speed zone

1e effects of concrete pressure (p0) at the beginningposition on the pressure drop trend along the concreteconveying are shown in Figure 9 Normalization of pressureduring concrete conveying based on p0 can decrease theinfluence of the air flow rate on the pressure measurementand the maximum error can be controlled within 2

During multiple experimental processes the value of αwas calculated by changing the air flow rate and feeding rateof concrete under different motor speeds

Accelerated pressure drop and uniform pressure dropduring the concrete conveying were predicted based on thevalue of α If α 1 the pressure drop caused by concretecollision and friction was the same in the constant speedsection If αlt 1 the pressure drop was relatively small be-cause of the low conveying speed of concrete In contrastαgt 1 indicates a high pressure drop because of the highconveying speed of concrete In the constant speed section ofconcrete particle collision was weak However particlecollision frequency was high and particle collision wasstrong in the accelerate zone resulting in the high energyloss of concrete particles 1erefore the pressure drop in theaccelerate zone was higher than that in the constant speedsection

1e difference between the experimental and theoreticalresults of concrete conveying was positively related to theconcrete throughput given the same flow rate of compressedair When the concrete throughput was small the experi-mental results and theoretical results were similar indicatingthat α was closer to 1 (Figure 10) With an increase ofconcrete throughput the difference of experimental andtheoretical results gradually increased 1e difference is thekey factor influencing the prediction of concrete conveying

Next the value of the transducer was fixed and theconcrete was input by the shotcrete machine at a constantfeeding rate Subsequently pressures at different points weretested by controlling the input of compressed air with the

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h

6m3h

Figure 8 Variation trend of concrete pressure

Stea

dy-s

tate

pre

ssur

e dro

p pe

run

it le

ngth

(Pa

m)

Concrete throughput4m3h5m3h6m3h

0

500

1000

1500

2000

2500

3000

38 42 46 50 54 58 62 66 7034Air flow rate (m3min)

Figure 7 Variations of pressure drop in the constant speed sectionwith air flow

Advances in Civil Engineering 7

regulating valve 1ere was a large difference between theexperimental results and theoretical results With an in-crease of air flow rate such differences decreased gradually1is difference was also a key factor that influenced theprediction of concrete conveying

Figures 10 and 11 show that the value of α had a directrelationship with concrete throughput and input of com-pressed air Tripathi et al tested materials of different grainsizes [29] and α can be defined as

α a + b middot eminus cmiddotμ

( 1113857 (19)

where μ mcmf is the ratio of concrete mass and air massExperimental data from Figures 11 and 12 were brought

into equation (19) yielding the following

α 12 + 011eminus 09μ

1113872 1113873 (20)

During the accelerated pressure drop experiment theconveying of concrete particles was accelerated at a specificspeed from one point and finally reached the movementtrend at a constant speed [30ndash32] 1e momentum equationwas used to calculate the pressure drop during this process

ΔPacc ΔPmom _ms middot Δuc

A

_ms middot ucss minus uc( 1113857

A (21)

Pressure drop is at equilibrium in the constant speedsection 1erefore the total accelerated pressure drop can begained from equations (18) (19) and (21) 1e totalaccelerated pressure drop was expressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961ΔPss +_ms middot ucss minus uc( 1113857

A

(22)

Also equations (1) and (2) were brought into equation(22) and thus the total accelerated pressure drop wasexpressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961 fDρfu2

f2D

L + ΔPc1113888 1113889

+_ms middot ucss minus uc( 1113857

A

(23)

To verify the accuracy of equation (20) the feedingrate of concrete was kept constant in the experiment 1econcrete-air ratio was changed by altering the air flow rateto analyze the pressure at different positions along theline Comparison between theoretical and experimental

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

65m3h

Figure 10 Comparison of theoretical and experimental pressuresafter adding α

Air flow

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

7m3min65m3min6m3min

55m3min

Figure 11 Comparison of pressure drop in the accelerate zone

ndash22

Air flowTheoretical trendExperimental trendError range

04

05

06

07

08

09

10

PP 0

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

Figure 9 Normalization trend under different wind speeds

8 Advances in Civil Engineering

pressures is shown in Figure 12 1e curve equationgained from the theoretical formula was similar to theexperimental results showing a maximum error of lessthan 10 1is verified the universality of equation (20)In this experiment pipe diameters of 20 inches and 25inches of the concrete line were applied Pressures atdifferent positions of the concrete line were tested by apressure transmitter (Figure 12) 1e maximum error wasless than 5 verifying the feasibility of equation (20)

5 Conclusions

In order to obtain the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying the concreteconveying pipeline was arranged to conduct the relatedconcrete conveying experiment 1e concrete was made upaccording to the common concrete ratio in the coal mineEach point pressure on the pipeline during the progress ofconveying was tested by the pressure transmitter set up onthe pipeline Also the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying was analyzed withmeasured pressure

1e results show that the pipeline pressure droppedrapidly at the beginning of the conveying and at the end ofthe bending pipe and the trend of the dropping linearly wasshowed gradually 1e accelerated pressure drop was ana-lyzed by combining experimental and momentum equationsduring concrete conveying 1e accelerated pressure dropwas analyzed which was mainly caused by accelerationfriction and the collision of concretes Also the friction andthe collision of concretes also exist in the zone of stableconvey

1e pressure drop curve was drawn according to thepressure at each point in the concrete conveying processAlso the mathematical model of pressure drop in theconcrete conveying process was set up To prevent random

interference factor from the friction and the collision andimproving the calculation accuracy the correction factor αwas introduced

Finally the measured pressures under different concretethroughputs and flow rates of compressed air were com-pared with the results from the mathematical model whichverified the accuracy of the mathematical model Also themain factors of pressure drop in the accelerate zone wereobtained as the ratio of the concrete mass and the com-pressed mass the initial velocity of the concrete the optimalfinal required velocity the feed speed of concrete and crosssection area of the conveying pipeline

Data Availability

1e data used to support the findings of this study areavailable from the corresponding author upon request

Additional Points

Innovations and highlights (1) Damage to the pressuretransmitter by concrete can be prevented by installing astrainer before the pressure transmitter (2) Variation laws ofpressure before and after the installation of a pressuretransmitter were studied by supplying air only (3) A sta-tistical analysis of the pressures at different positions alongthe concrete conveying line under different input quantitiesof concrete and compressed air was performed Based onthis the law of pressure drop during the conveying ofconcrete was discussed (4) 1e pressure drop in the lineduring the conveying of concrete was predicted

Conflicts of Interest

1e authors declare that they have no conflicts of interest

References

[1] L Chen G LiuW Cheng and G Pan ldquoPipe flow of pumpingwet shotcrete based on lubrication layerrdquo SpringerPlus vol 5no 1 p 945 2016

[2] Y Cai Y Jiang I Djamaluddin T Iura and T Esaki ldquoAnanalytical model considering interaction behavior of groutedrock bolts for convergence-confinement method in tunnelingdesignrdquo International Journal of Rock Mechanics and MiningSciences vol 76 pp 112ndash126 2015

[3] L Chen P Li G Liu W Cheng and Z Liu ldquoDevelopment ofcement dust suppression technology during shotcrete in mineof China-a reviewrdquo Journal of Loss Prevention in the ProcessIndustries vol 55 pp 232ndash242 2018

[4] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[5] Q Liu W Nie Y Hua H Peng and Z Liu ldquo1e effects of theinstallation position of a multi-radial swirling air-curtaingenerator on dust diffusion and pollution rules in a fully-mechanized excavation face a case studyrdquo Powder Technol-ogy vol 329 pp 371ndash385 2018

[6] R Naveh N M Tripathi and H Kalman ldquoExperimentalpressure drop analysis for horizontal dilute phase particle-fluid flowsrdquo Powder Technology vol 321 pp 353ndash368 2017

Pipe diameter

3

2inch25inch

Theoretical trendExperimental trend

5

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

Figure 12 Pressure drop at different specifications of concretelines

Advances in Civil Engineering 9

[7] O G Brown ldquo1e history of the Darcy-Weisbach equationfor pipe flow resistancerdquo in Proceedings of the Environmentaland Water Resources History pp 34ndash43 Washington DCUSA November 2003

[8] O Molerus ldquoOverview pneumatic transport of solidsrdquoPowder Technology vol 88 no 3 pp 309ndash321 1996

[9] Q LiuW Nie Y Hua H Peng C Liu and CWei ldquoResearchon tunnel ventilation systems dust diffusion and pollutionbehaviour by air curtains based on CFD technology and fieldmeasurementrdquo Building and Environment vol 147pp 444ndash460 2019

[10] Y-Q Zhang J-L Zhu X-H Wang X-W ZhangS-X Zhou and P Liang ldquoSimulation of large coal particlespyrolysis by circulating ash heat carrier toward the axialdimension of the moving bedrdquo Fuel Processing Technologyvol 154 pp 227ndash234 2016

[11] Y Tomita H Tashiro K Deguchi and T Jotaki ldquoSuddenexpansion of gas-solid two-phase flow in a piperdquo Physics ofFluids vol 23 no 4 pp 663ndash666 1980

[12] P Li Z Zhou L Chen G Liu and W Xiao ldquoResearch ondust suppression technology of shotcrete based on new sprayequipment and process optimizationrdquo Advances in CivilEngineering vol 2019 Article ID 4831215 11 pages 2019

[13] B Kong E Wang and Z Li ldquo1e effect of high temperatureenvironment on rock propertiesmdashan example of electro-magnetic radiation characterizationrdquo Environmental Scienceand Pollution Research vol 25 no 29 pp 1ndash11 2018

[14] A Shimizu R Echigo S Hasegawa and M Hishida ldquoEx-perimental study on the pressure drop and the entry length ofthe gas-solid suspension flow in a circular tuberdquo InternationalJournal of Multiphase Flow vol 4 no 1 pp 53ndash64 1978

[15] N Guanhua D Kai L Shang and S Qian ldquoGas desorptioncharacteristics effected by the pulsating hydraulic fracturingin coalrdquo Fuel vol 236 pp 190ndash200 2019

[16] G Zhou Y Ma T Fan and G Wang ldquoPreparation andcharacteristics of a multifunctional dust suppressant withagglomeration and wettability performance used in coalminerdquo Chemical Engineering Research and Design vol 132pp 729ndash742 2018

[17] R D Marcus J D Hilbert Jr and G E Klinzing ldquoFlowthrough bends and acceleration zones in pneumatic con-veying systemsrdquo Bulk Solids Handling vol 5 no 4 pp 121ndash126 1985

[18] T Fan G Zhou and J Wang ldquoPreparation and character-ization of a wetting-agglomeration-based hybrid coal dustsuppressantrdquo Process Safety and Environmental Protectionvol 113 pp 282ndash291 2018

[19] R A Duckworth Empirical Correlations Fore Dilute PhaseDepartment of Chemical Engineering 1e University ofQueensland Brisbane Australia Lecture notes CSIROMineral engineering 1969

[20] Y Tomita and H Tashiro ldquoLoss coefficient for abrupt en-largement in pneumatic transport of solids in pipesrdquo BulkSolid Handling vol 8 pp 129ndash131 1988

[21] J A Ottjes ldquoDigital simulation of pneumatic particletransportrdquo Chemical Engineering Science vol 33 no 6pp 783ndash786 1978

[22] H V Nguyen R Yokota G Stenchikov et al ldquoA paralleldirect numerical simulation of dust particles in a turbulentflowrdquo in Proceedings of the EGU General Assembly ConferenceAbstracts Vienna Austria April 2012

[23] N Huber and M Sommerfeld ldquoModelling and numericalcalculation of dilute-phase pneumatic conveying in pipesystemsrdquo Powder Technology vol 99 no 1 pp 90ndash101 1998

[24] K J Hanley E P Byrne and K Cronin ldquoProbabilisticanalysis of particle impact at a pipe bend in pneumaticconveyingrdquo Powder Technology vol 233 pp 176ndash185 2013

[25] G E Klinzing and O M Basha ldquoA correlation for particlevelocities in pneumatic conveyingrdquo Powder Technologyvol 310 pp 201ndash204 2017

[26] H G Merkus and G M H Meesters ldquoProduction handlingand characterization of particulate materialsrdquo Particle Tech-nology vol 11 no 4 pp 619ndash629 2016

[27] G Liu W Cheng and L Chen ldquoInvestigating and optimizingthe mix proportion of pumping wet-mix shotcrete withpolypropylene fiberrdquo Construction and Building Materialsvol 150 pp 14ndash23 2017

[28] W Wei G Qingliang W Yuxin Y Hairui Z Jiansheng andL Junfu ldquoExperimental study on the solid velocity in hori-zontal dilute phase pneumatic conveying of fine powdersrdquoPowder Technology vol 212 no 3 pp 403ndash409 2011

[29] N M Tripathi A Levy and H Kalman ldquoAccelerationpressure drop analysis in horizontal dilute phase pneumaticconveying systemrdquo Powder Technology vol 327 pp 43ndash562018

[30] L Chen G Ma G Liu and Z Liu ldquoEffect of pumping andspraying processes on the rheological properties and aircontent of wet-mix shotcrete with various admixturesrdquoConstruction and Building Materials vol 225 pp 311ndash3232019

[31] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[32] B Kong E Wang W Lu and Z Li ldquoApplication of elec-tromagnetic radiation detection in high-temperature anom-alous areas experiencing coalfield firesrdquo Energy vol 189Article ID 116144 2019

10 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

regulating valve 1ere was a large difference between theexperimental results and theoretical results With an in-crease of air flow rate such differences decreased gradually1is difference was also a key factor that influenced theprediction of concrete conveying

Figures 10 and 11 show that the value of α had a directrelationship with concrete throughput and input of com-pressed air Tripathi et al tested materials of different grainsizes [29] and α can be defined as

α a + b middot eminus cmiddotμ

( 1113857 (19)

where μ mcmf is the ratio of concrete mass and air massExperimental data from Figures 11 and 12 were brought

into equation (19) yielding the following

α 12 + 011eminus 09μ

1113872 1113873 (20)

During the accelerated pressure drop experiment theconveying of concrete particles was accelerated at a specificspeed from one point and finally reached the movementtrend at a constant speed [30ndash32] 1e momentum equationwas used to calculate the pressure drop during this process

ΔPacc ΔPmom _ms middot Δuc

A

_ms middot ucss minus uc( 1113857

A (21)

Pressure drop is at equilibrium in the constant speedsection 1erefore the total accelerated pressure drop can begained from equations (18) (19) and (21) 1e totalaccelerated pressure drop was expressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961ΔPss +_ms middot ucss minus uc( 1113857

A

(22)

Also equations (1) and (2) were brought into equation(22) and thus the total accelerated pressure drop wasexpressed as

ΔPacctotal 12 + 011eminus 09μ

1113872 11138731113960 1113961 fDρfu2

f2D

L + ΔPc1113888 1113889

+_ms middot ucss minus uc( 1113857

A

(23)

To verify the accuracy of equation (20) the feedingrate of concrete was kept constant in the experiment 1econcrete-air ratio was changed by altering the air flow rateto analyze the pressure at different positions along theline Comparison between theoretical and experimental

Concrete throughput

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

65m3h

Figure 10 Comparison of theoretical and experimental pressuresafter adding α

Air flow

Theoretical trendExperimental trend

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

7m3min65m3min6m3min

55m3min

Figure 11 Comparison of pressure drop in the accelerate zone

ndash22

Air flowTheoretical trendExperimental trendError range

04

05

06

07

08

09

10

PP 0

18 2012102 40 16146 8Distance (m)

45m3h5m3h55m3h6m3h

Figure 9 Normalization trend under different wind speeds

8 Advances in Civil Engineering

pressures is shown in Figure 12 1e curve equationgained from the theoretical formula was similar to theexperimental results showing a maximum error of lessthan 10 1is verified the universality of equation (20)In this experiment pipe diameters of 20 inches and 25inches of the concrete line were applied Pressures atdifferent positions of the concrete line were tested by apressure transmitter (Figure 12) 1e maximum error wasless than 5 verifying the feasibility of equation (20)

5 Conclusions

In order to obtain the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying the concreteconveying pipeline was arranged to conduct the relatedconcrete conveying experiment 1e concrete was made upaccording to the common concrete ratio in the coal mineEach point pressure on the pipeline during the progress ofconveying was tested by the pressure transmitter set up onthe pipeline Also the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying was analyzed withmeasured pressure

1e results show that the pipeline pressure droppedrapidly at the beginning of the conveying and at the end ofthe bending pipe and the trend of the dropping linearly wasshowed gradually 1e accelerated pressure drop was ana-lyzed by combining experimental and momentum equationsduring concrete conveying 1e accelerated pressure dropwas analyzed which was mainly caused by accelerationfriction and the collision of concretes Also the friction andthe collision of concretes also exist in the zone of stableconvey

1e pressure drop curve was drawn according to thepressure at each point in the concrete conveying processAlso the mathematical model of pressure drop in theconcrete conveying process was set up To prevent random

interference factor from the friction and the collision andimproving the calculation accuracy the correction factor αwas introduced

Finally the measured pressures under different concretethroughputs and flow rates of compressed air were com-pared with the results from the mathematical model whichverified the accuracy of the mathematical model Also themain factors of pressure drop in the accelerate zone wereobtained as the ratio of the concrete mass and the com-pressed mass the initial velocity of the concrete the optimalfinal required velocity the feed speed of concrete and crosssection area of the conveying pipeline

Data Availability

1e data used to support the findings of this study areavailable from the corresponding author upon request

Additional Points

Innovations and highlights (1) Damage to the pressuretransmitter by concrete can be prevented by installing astrainer before the pressure transmitter (2) Variation laws ofpressure before and after the installation of a pressuretransmitter were studied by supplying air only (3) A sta-tistical analysis of the pressures at different positions alongthe concrete conveying line under different input quantitiesof concrete and compressed air was performed Based onthis the law of pressure drop during the conveying ofconcrete was discussed (4) 1e pressure drop in the lineduring the conveying of concrete was predicted

Conflicts of Interest

1e authors declare that they have no conflicts of interest

References

[1] L Chen G LiuW Cheng and G Pan ldquoPipe flow of pumpingwet shotcrete based on lubrication layerrdquo SpringerPlus vol 5no 1 p 945 2016

[2] Y Cai Y Jiang I Djamaluddin T Iura and T Esaki ldquoAnanalytical model considering interaction behavior of groutedrock bolts for convergence-confinement method in tunnelingdesignrdquo International Journal of Rock Mechanics and MiningSciences vol 76 pp 112ndash126 2015

[3] L Chen P Li G Liu W Cheng and Z Liu ldquoDevelopment ofcement dust suppression technology during shotcrete in mineof China-a reviewrdquo Journal of Loss Prevention in the ProcessIndustries vol 55 pp 232ndash242 2018

[4] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[5] Q Liu W Nie Y Hua H Peng and Z Liu ldquo1e effects of theinstallation position of a multi-radial swirling air-curtaingenerator on dust diffusion and pollution rules in a fully-mechanized excavation face a case studyrdquo Powder Technol-ogy vol 329 pp 371ndash385 2018

[6] R Naveh N M Tripathi and H Kalman ldquoExperimentalpressure drop analysis for horizontal dilute phase particle-fluid flowsrdquo Powder Technology vol 321 pp 353ndash368 2017

Pipe diameter

3

2inch25inch

Theoretical trendExperimental trend

5

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

Figure 12 Pressure drop at different specifications of concretelines

Advances in Civil Engineering 9

[7] O G Brown ldquo1e history of the Darcy-Weisbach equationfor pipe flow resistancerdquo in Proceedings of the Environmentaland Water Resources History pp 34ndash43 Washington DCUSA November 2003

[8] O Molerus ldquoOverview pneumatic transport of solidsrdquoPowder Technology vol 88 no 3 pp 309ndash321 1996

[9] Q LiuW Nie Y Hua H Peng C Liu and CWei ldquoResearchon tunnel ventilation systems dust diffusion and pollutionbehaviour by air curtains based on CFD technology and fieldmeasurementrdquo Building and Environment vol 147pp 444ndash460 2019

[10] Y-Q Zhang J-L Zhu X-H Wang X-W ZhangS-X Zhou and P Liang ldquoSimulation of large coal particlespyrolysis by circulating ash heat carrier toward the axialdimension of the moving bedrdquo Fuel Processing Technologyvol 154 pp 227ndash234 2016

[11] Y Tomita H Tashiro K Deguchi and T Jotaki ldquoSuddenexpansion of gas-solid two-phase flow in a piperdquo Physics ofFluids vol 23 no 4 pp 663ndash666 1980

[12] P Li Z Zhou L Chen G Liu and W Xiao ldquoResearch ondust suppression technology of shotcrete based on new sprayequipment and process optimizationrdquo Advances in CivilEngineering vol 2019 Article ID 4831215 11 pages 2019

[13] B Kong E Wang and Z Li ldquo1e effect of high temperatureenvironment on rock propertiesmdashan example of electro-magnetic radiation characterizationrdquo Environmental Scienceand Pollution Research vol 25 no 29 pp 1ndash11 2018

[14] A Shimizu R Echigo S Hasegawa and M Hishida ldquoEx-perimental study on the pressure drop and the entry length ofthe gas-solid suspension flow in a circular tuberdquo InternationalJournal of Multiphase Flow vol 4 no 1 pp 53ndash64 1978

[15] N Guanhua D Kai L Shang and S Qian ldquoGas desorptioncharacteristics effected by the pulsating hydraulic fracturingin coalrdquo Fuel vol 236 pp 190ndash200 2019

[16] G Zhou Y Ma T Fan and G Wang ldquoPreparation andcharacteristics of a multifunctional dust suppressant withagglomeration and wettability performance used in coalminerdquo Chemical Engineering Research and Design vol 132pp 729ndash742 2018

[17] R D Marcus J D Hilbert Jr and G E Klinzing ldquoFlowthrough bends and acceleration zones in pneumatic con-veying systemsrdquo Bulk Solids Handling vol 5 no 4 pp 121ndash126 1985

[18] T Fan G Zhou and J Wang ldquoPreparation and character-ization of a wetting-agglomeration-based hybrid coal dustsuppressantrdquo Process Safety and Environmental Protectionvol 113 pp 282ndash291 2018

[19] R A Duckworth Empirical Correlations Fore Dilute PhaseDepartment of Chemical Engineering 1e University ofQueensland Brisbane Australia Lecture notes CSIROMineral engineering 1969

[20] Y Tomita and H Tashiro ldquoLoss coefficient for abrupt en-largement in pneumatic transport of solids in pipesrdquo BulkSolid Handling vol 8 pp 129ndash131 1988

[21] J A Ottjes ldquoDigital simulation of pneumatic particletransportrdquo Chemical Engineering Science vol 33 no 6pp 783ndash786 1978

[22] H V Nguyen R Yokota G Stenchikov et al ldquoA paralleldirect numerical simulation of dust particles in a turbulentflowrdquo in Proceedings of the EGU General Assembly ConferenceAbstracts Vienna Austria April 2012

[23] N Huber and M Sommerfeld ldquoModelling and numericalcalculation of dilute-phase pneumatic conveying in pipesystemsrdquo Powder Technology vol 99 no 1 pp 90ndash101 1998

[24] K J Hanley E P Byrne and K Cronin ldquoProbabilisticanalysis of particle impact at a pipe bend in pneumaticconveyingrdquo Powder Technology vol 233 pp 176ndash185 2013

[25] G E Klinzing and O M Basha ldquoA correlation for particlevelocities in pneumatic conveyingrdquo Powder Technologyvol 310 pp 201ndash204 2017

[26] H G Merkus and G M H Meesters ldquoProduction handlingand characterization of particulate materialsrdquo Particle Tech-nology vol 11 no 4 pp 619ndash629 2016

[27] G Liu W Cheng and L Chen ldquoInvestigating and optimizingthe mix proportion of pumping wet-mix shotcrete withpolypropylene fiberrdquo Construction and Building Materialsvol 150 pp 14ndash23 2017

[28] W Wei G Qingliang W Yuxin Y Hairui Z Jiansheng andL Junfu ldquoExperimental study on the solid velocity in hori-zontal dilute phase pneumatic conveying of fine powdersrdquoPowder Technology vol 212 no 3 pp 403ndash409 2011

[29] N M Tripathi A Levy and H Kalman ldquoAccelerationpressure drop analysis in horizontal dilute phase pneumaticconveying systemrdquo Powder Technology vol 327 pp 43ndash562018

[30] L Chen G Ma G Liu and Z Liu ldquoEffect of pumping andspraying processes on the rheological properties and aircontent of wet-mix shotcrete with various admixturesrdquoConstruction and Building Materials vol 225 pp 311ndash3232019

[31] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[32] B Kong E Wang W Lu and Z Li ldquoApplication of elec-tromagnetic radiation detection in high-temperature anom-alous areas experiencing coalfield firesrdquo Energy vol 189Article ID 116144 2019

10 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

pressures is shown in Figure 12 1e curve equationgained from the theoretical formula was similar to theexperimental results showing a maximum error of lessthan 10 1is verified the universality of equation (20)In this experiment pipe diameters of 20 inches and 25inches of the concrete line were applied Pressures atdifferent positions of the concrete line were tested by apressure transmitter (Figure 12) 1e maximum error wasless than 5 verifying the feasibility of equation (20)

5 Conclusions

In order to obtain the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying the concreteconveying pipeline was arranged to conduct the relatedconcrete conveying experiment 1e concrete was made upaccording to the common concrete ratio in the coal mineEach point pressure on the pipeline during the progress ofconveying was tested by the pressure transmitter set up onthe pipeline Also the pressure drop in the accelerate zone ofhorizontal conveying of concrete spraying was analyzed withmeasured pressure

1e results show that the pipeline pressure droppedrapidly at the beginning of the conveying and at the end ofthe bending pipe and the trend of the dropping linearly wasshowed gradually 1e accelerated pressure drop was ana-lyzed by combining experimental and momentum equationsduring concrete conveying 1e accelerated pressure dropwas analyzed which was mainly caused by accelerationfriction and the collision of concretes Also the friction andthe collision of concretes also exist in the zone of stableconvey

1e pressure drop curve was drawn according to thepressure at each point in the concrete conveying processAlso the mathematical model of pressure drop in theconcrete conveying process was set up To prevent random

interference factor from the friction and the collision andimproving the calculation accuracy the correction factor αwas introduced

Finally the measured pressures under different concretethroughputs and flow rates of compressed air were com-pared with the results from the mathematical model whichverified the accuracy of the mathematical model Also themain factors of pressure drop in the accelerate zone wereobtained as the ratio of the concrete mass and the com-pressed mass the initial velocity of the concrete the optimalfinal required velocity the feed speed of concrete and crosssection area of the conveying pipeline

Data Availability

1e data used to support the findings of this study areavailable from the corresponding author upon request

Additional Points

Innovations and highlights (1) Damage to the pressuretransmitter by concrete can be prevented by installing astrainer before the pressure transmitter (2) Variation laws ofpressure before and after the installation of a pressuretransmitter were studied by supplying air only (3) A sta-tistical analysis of the pressures at different positions alongthe concrete conveying line under different input quantitiesof concrete and compressed air was performed Based onthis the law of pressure drop during the conveying ofconcrete was discussed (4) 1e pressure drop in the lineduring the conveying of concrete was predicted

Conflicts of Interest

1e authors declare that they have no conflicts of interest

References

[1] L Chen G LiuW Cheng and G Pan ldquoPipe flow of pumpingwet shotcrete based on lubrication layerrdquo SpringerPlus vol 5no 1 p 945 2016

[2] Y Cai Y Jiang I Djamaluddin T Iura and T Esaki ldquoAnanalytical model considering interaction behavior of groutedrock bolts for convergence-confinement method in tunnelingdesignrdquo International Journal of Rock Mechanics and MiningSciences vol 76 pp 112ndash126 2015

[3] L Chen P Li G Liu W Cheng and Z Liu ldquoDevelopment ofcement dust suppression technology during shotcrete in mineof China-a reviewrdquo Journal of Loss Prevention in the ProcessIndustries vol 55 pp 232ndash242 2018

[4] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[5] Q Liu W Nie Y Hua H Peng and Z Liu ldquo1e effects of theinstallation position of a multi-radial swirling air-curtaingenerator on dust diffusion and pollution rules in a fully-mechanized excavation face a case studyrdquo Powder Technol-ogy vol 329 pp 371ndash385 2018

[6] R Naveh N M Tripathi and H Kalman ldquoExperimentalpressure drop analysis for horizontal dilute phase particle-fluid flowsrdquo Powder Technology vol 321 pp 353ndash368 2017

Pipe diameter

3

2inch25inch

Theoretical trendExperimental trend

5

260

270

280

290

300

310

320

330

340

350

Pres

sure

(kPa

)

18 2012102 40 16146 8Distance (m)

Figure 12 Pressure drop at different specifications of concretelines

Advances in Civil Engineering 9

[7] O G Brown ldquo1e history of the Darcy-Weisbach equationfor pipe flow resistancerdquo in Proceedings of the Environmentaland Water Resources History pp 34ndash43 Washington DCUSA November 2003

[8] O Molerus ldquoOverview pneumatic transport of solidsrdquoPowder Technology vol 88 no 3 pp 309ndash321 1996

[9] Q LiuW Nie Y Hua H Peng C Liu and CWei ldquoResearchon tunnel ventilation systems dust diffusion and pollutionbehaviour by air curtains based on CFD technology and fieldmeasurementrdquo Building and Environment vol 147pp 444ndash460 2019

[10] Y-Q Zhang J-L Zhu X-H Wang X-W ZhangS-X Zhou and P Liang ldquoSimulation of large coal particlespyrolysis by circulating ash heat carrier toward the axialdimension of the moving bedrdquo Fuel Processing Technologyvol 154 pp 227ndash234 2016

[11] Y Tomita H Tashiro K Deguchi and T Jotaki ldquoSuddenexpansion of gas-solid two-phase flow in a piperdquo Physics ofFluids vol 23 no 4 pp 663ndash666 1980

[12] P Li Z Zhou L Chen G Liu and W Xiao ldquoResearch ondust suppression technology of shotcrete based on new sprayequipment and process optimizationrdquo Advances in CivilEngineering vol 2019 Article ID 4831215 11 pages 2019

[13] B Kong E Wang and Z Li ldquo1e effect of high temperatureenvironment on rock propertiesmdashan example of electro-magnetic radiation characterizationrdquo Environmental Scienceand Pollution Research vol 25 no 29 pp 1ndash11 2018

[14] A Shimizu R Echigo S Hasegawa and M Hishida ldquoEx-perimental study on the pressure drop and the entry length ofthe gas-solid suspension flow in a circular tuberdquo InternationalJournal of Multiphase Flow vol 4 no 1 pp 53ndash64 1978

[15] N Guanhua D Kai L Shang and S Qian ldquoGas desorptioncharacteristics effected by the pulsating hydraulic fracturingin coalrdquo Fuel vol 236 pp 190ndash200 2019

[16] G Zhou Y Ma T Fan and G Wang ldquoPreparation andcharacteristics of a multifunctional dust suppressant withagglomeration and wettability performance used in coalminerdquo Chemical Engineering Research and Design vol 132pp 729ndash742 2018

[17] R D Marcus J D Hilbert Jr and G E Klinzing ldquoFlowthrough bends and acceleration zones in pneumatic con-veying systemsrdquo Bulk Solids Handling vol 5 no 4 pp 121ndash126 1985

[18] T Fan G Zhou and J Wang ldquoPreparation and character-ization of a wetting-agglomeration-based hybrid coal dustsuppressantrdquo Process Safety and Environmental Protectionvol 113 pp 282ndash291 2018

[19] R A Duckworth Empirical Correlations Fore Dilute PhaseDepartment of Chemical Engineering 1e University ofQueensland Brisbane Australia Lecture notes CSIROMineral engineering 1969

[20] Y Tomita and H Tashiro ldquoLoss coefficient for abrupt en-largement in pneumatic transport of solids in pipesrdquo BulkSolid Handling vol 8 pp 129ndash131 1988

[21] J A Ottjes ldquoDigital simulation of pneumatic particletransportrdquo Chemical Engineering Science vol 33 no 6pp 783ndash786 1978

[22] H V Nguyen R Yokota G Stenchikov et al ldquoA paralleldirect numerical simulation of dust particles in a turbulentflowrdquo in Proceedings of the EGU General Assembly ConferenceAbstracts Vienna Austria April 2012

[23] N Huber and M Sommerfeld ldquoModelling and numericalcalculation of dilute-phase pneumatic conveying in pipesystemsrdquo Powder Technology vol 99 no 1 pp 90ndash101 1998

[24] K J Hanley E P Byrne and K Cronin ldquoProbabilisticanalysis of particle impact at a pipe bend in pneumaticconveyingrdquo Powder Technology vol 233 pp 176ndash185 2013

[25] G E Klinzing and O M Basha ldquoA correlation for particlevelocities in pneumatic conveyingrdquo Powder Technologyvol 310 pp 201ndash204 2017

[26] H G Merkus and G M H Meesters ldquoProduction handlingand characterization of particulate materialsrdquo Particle Tech-nology vol 11 no 4 pp 619ndash629 2016

[27] G Liu W Cheng and L Chen ldquoInvestigating and optimizingthe mix proportion of pumping wet-mix shotcrete withpolypropylene fiberrdquo Construction and Building Materialsvol 150 pp 14ndash23 2017

[28] W Wei G Qingliang W Yuxin Y Hairui Z Jiansheng andL Junfu ldquoExperimental study on the solid velocity in hori-zontal dilute phase pneumatic conveying of fine powdersrdquoPowder Technology vol 212 no 3 pp 403ndash409 2011

[29] N M Tripathi A Levy and H Kalman ldquoAccelerationpressure drop analysis in horizontal dilute phase pneumaticconveying systemrdquo Powder Technology vol 327 pp 43ndash562018

[30] L Chen G Ma G Liu and Z Liu ldquoEffect of pumping andspraying processes on the rheological properties and aircontent of wet-mix shotcrete with various admixturesrdquoConstruction and Building Materials vol 225 pp 311ndash3232019

[31] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[32] B Kong E Wang W Lu and Z Li ldquoApplication of elec-tromagnetic radiation detection in high-temperature anom-alous areas experiencing coalfield firesrdquo Energy vol 189Article ID 116144 2019

10 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

[7] O G Brown ldquo1e history of the Darcy-Weisbach equationfor pipe flow resistancerdquo in Proceedings of the Environmentaland Water Resources History pp 34ndash43 Washington DCUSA November 2003

[8] O Molerus ldquoOverview pneumatic transport of solidsrdquoPowder Technology vol 88 no 3 pp 309ndash321 1996

[9] Q LiuW Nie Y Hua H Peng C Liu and CWei ldquoResearchon tunnel ventilation systems dust diffusion and pollutionbehaviour by air curtains based on CFD technology and fieldmeasurementrdquo Building and Environment vol 147pp 444ndash460 2019

[10] Y-Q Zhang J-L Zhu X-H Wang X-W ZhangS-X Zhou and P Liang ldquoSimulation of large coal particlespyrolysis by circulating ash heat carrier toward the axialdimension of the moving bedrdquo Fuel Processing Technologyvol 154 pp 227ndash234 2016

[11] Y Tomita H Tashiro K Deguchi and T Jotaki ldquoSuddenexpansion of gas-solid two-phase flow in a piperdquo Physics ofFluids vol 23 no 4 pp 663ndash666 1980

[12] P Li Z Zhou L Chen G Liu and W Xiao ldquoResearch ondust suppression technology of shotcrete based on new sprayequipment and process optimizationrdquo Advances in CivilEngineering vol 2019 Article ID 4831215 11 pages 2019

[13] B Kong E Wang and Z Li ldquo1e effect of high temperatureenvironment on rock propertiesmdashan example of electro-magnetic radiation characterizationrdquo Environmental Scienceand Pollution Research vol 25 no 29 pp 1ndash11 2018

[14] A Shimizu R Echigo S Hasegawa and M Hishida ldquoEx-perimental study on the pressure drop and the entry length ofthe gas-solid suspension flow in a circular tuberdquo InternationalJournal of Multiphase Flow vol 4 no 1 pp 53ndash64 1978

[15] N Guanhua D Kai L Shang and S Qian ldquoGas desorptioncharacteristics effected by the pulsating hydraulic fracturingin coalrdquo Fuel vol 236 pp 190ndash200 2019

[16] G Zhou Y Ma T Fan and G Wang ldquoPreparation andcharacteristics of a multifunctional dust suppressant withagglomeration and wettability performance used in coalminerdquo Chemical Engineering Research and Design vol 132pp 729ndash742 2018

[17] R D Marcus J D Hilbert Jr and G E Klinzing ldquoFlowthrough bends and acceleration zones in pneumatic con-veying systemsrdquo Bulk Solids Handling vol 5 no 4 pp 121ndash126 1985

[18] T Fan G Zhou and J Wang ldquoPreparation and character-ization of a wetting-agglomeration-based hybrid coal dustsuppressantrdquo Process Safety and Environmental Protectionvol 113 pp 282ndash291 2018

[19] R A Duckworth Empirical Correlations Fore Dilute PhaseDepartment of Chemical Engineering 1e University ofQueensland Brisbane Australia Lecture notes CSIROMineral engineering 1969

[20] Y Tomita and H Tashiro ldquoLoss coefficient for abrupt en-largement in pneumatic transport of solids in pipesrdquo BulkSolid Handling vol 8 pp 129ndash131 1988

[21] J A Ottjes ldquoDigital simulation of pneumatic particletransportrdquo Chemical Engineering Science vol 33 no 6pp 783ndash786 1978

[22] H V Nguyen R Yokota G Stenchikov et al ldquoA paralleldirect numerical simulation of dust particles in a turbulentflowrdquo in Proceedings of the EGU General Assembly ConferenceAbstracts Vienna Austria April 2012

[23] N Huber and M Sommerfeld ldquoModelling and numericalcalculation of dilute-phase pneumatic conveying in pipesystemsrdquo Powder Technology vol 99 no 1 pp 90ndash101 1998

[24] K J Hanley E P Byrne and K Cronin ldquoProbabilisticanalysis of particle impact at a pipe bend in pneumaticconveyingrdquo Powder Technology vol 233 pp 176ndash185 2013

[25] G E Klinzing and O M Basha ldquoA correlation for particlevelocities in pneumatic conveyingrdquo Powder Technologyvol 310 pp 201ndash204 2017

[26] H G Merkus and G M H Meesters ldquoProduction handlingand characterization of particulate materialsrdquo Particle Tech-nology vol 11 no 4 pp 619ndash629 2016

[27] G Liu W Cheng and L Chen ldquoInvestigating and optimizingthe mix proportion of pumping wet-mix shotcrete withpolypropylene fiberrdquo Construction and Building Materialsvol 150 pp 14ndash23 2017

[28] W Wei G Qingliang W Yuxin Y Hairui Z Jiansheng andL Junfu ldquoExperimental study on the solid velocity in hori-zontal dilute phase pneumatic conveying of fine powdersrdquoPowder Technology vol 212 no 3 pp 403ndash409 2011

[29] N M Tripathi A Levy and H Kalman ldquoAccelerationpressure drop analysis in horizontal dilute phase pneumaticconveying systemrdquo Powder Technology vol 327 pp 43ndash562018

[30] L Chen G Ma G Liu and Z Liu ldquoEffect of pumping andspraying processes on the rheological properties and aircontent of wet-mix shotcrete with various admixturesrdquoConstruction and Building Materials vol 225 pp 311ndash3232019

[31] L Chen and G Liu ldquoAirflow-dust migration law and controltechnology under the simultaneous operations of shotcretingand drilling in roadwaysrdquo Arabian Journal for Science andEngineering vol 44 no 5 pp 4961ndash4969 2019

[32] B Kong E Wang W Lu and Z Li ldquoApplication of elec-tromagnetic radiation detection in high-temperature anom-alous areas experiencing coalfield firesrdquo Energy vol 189Article ID 116144 2019

10 Advances in Civil Engineering

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Active and Passive Electronic Components

VLSI Design

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Shock and Vibration

Hindawiwwwhindawicom Volume 2018

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom

Journal ofEngineeringVolume 2018

SensorsJournal of

Hindawiwwwhindawicom Volume 2018

International Journal of

RotatingMachinery

Hindawiwwwhindawicom Volume 2018

Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Navigation and Observation

International Journal of

Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom