ijgsw 2015 vol

IJGSW 2015 Vol.2

2015 Vol.2

The Chief Editor

Sun Jichao University of Wisconsin-Milwaukee, USA

China University of Geosciences, China

Associate Editors:

Todd M. Davis, P.E. Milwaukee School of Engineering, USA

Rajan Saha University of Wisconsin-Milwaukee, USA

Marina Ivanovna Kozhukhova University of Wisconsin-Milwaukee, USA

Yang Jishan Yellow River Institute of Hydraulic Research, China

Huang Wendian Sichuan University, China

Huang Guoxian Cardiff University, UK

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INTERNATIONAL JOURNAL OF

GROUND SEDIMENT & WATER

Research Paper: 1. Analysis of lateral soil pressures for reinforced earth retaining wall based on tensile failure

.........................................................................................................................................................15-21

Sun Wen-jun, Song Yang, Guo Ke-xin, Zhu Xiao-yun

2. Mechanical analysis of flexible base durable asphalt pavement structure..............................22-31

Song Yang, Sun Wen-jun, Zhu Xiao-yun, Zhang Hai-feng

3. Erosion and sediment yield time-space distribution characteristics research of slope-gully

system based on simulated rainfall..............................................................................................32-40

Fan Dong-ming, Yang Chun-xia, Wu Qing, Wang Jia-xin, Yang Ji-shan

4. Simplify the structure of the surface mining and analytic calculation.....................................41-51

Zhang Mei, Meng Da

5. Based on the perspective of construction contract of project quality management research

.........................................................................................................................................................52-58

Yang Xiao-liang

ISSN:2372-0743 print ISSN:2373-2989 on line

International Journal of Ground Sediment & Water Vol. 022015

Journal Website: http://ijgsw.comze.com/ You can submit your paper to email: [email protected]

- 15 -

Analysis of Lateral Soil Pressures for Reinforced Earth Retaining Wall Based on Tensile Failure

Sun Wen-jun1,2, Song Yang1,2*, Guo Ke-xin1,2, Zhu Xiao-yun3

1. Hebei Engineering and Technical College, Cangzhou, Hebei, 061001, China 2. College of Civil Engineering, Hebei University of Technology, Tianjin 300401, China 3. Tianjin transportation vocational college, Tianjin, 300110, China

Abstract: Considering the effect of reinforcement, and applying the cohesive force theory

and Coulomb's earth pressure theory, thus the tensile failure theoretical formulae of lateral soil

pressure for reinforced earth retaining wall is obtained. Analytical results show that cohesive

force of reinforced earth has increment for the tensile failure. The lateral soil pressures value

of wall back using proposed formula are smaller than using classical earth pressure theories of

variable coefficient method. And the lateral soil pressure will increase with increasing of

vertical spacing of reinforcement and decrease with increasing of the tensile strength of the

reinforcement. The calculating results of this proposing method basically accord to results of

the site tests in geogrid reinforced earth retaining wall.

Keywords: strength model, lateral soil pressure, reinforced earth retaining wall, vertical

spacing, tensile failure

1 Introduction

The key of reinforced earth retaining wall’s design is the calculation of reinforcement’s tensile force. The tensile force is provided by the frictional resistance between there reinforcement sand soil. And soil pressure on the wall panel is equal to frictional resistance between there reinforcement sand soil[1-2]. Therefore, the key of reinforced earth retaining wall’s design is to determine the soil pressure of wall back. There are the Coulomb force law, Coulomb method of moment, normal stress uniform distribution method, normal stress trapezoidal distribution method, Medvedev normal stress distribution method, Osman energy method, empirical method and highway variable coefficient method[2] and some other methods to calculate soil pressure of wall back currently. These methods almost adopt the Rankine's earth pressure theory formula and amended its coefficient of earth pressure. The highway variable coefficient method can explain some of the actual condition of earth pressure distribution more reason ably compared with other methods. So it is widely used in

◆Research Paper◆




- 16 -

the design of reinforced earth retaining wall. Yin Yaxiong[3],Wang Xiang [4], ,Yang Guangqing[5] etc. carried out the field study on reinforced earth retaining wall. AndT ang Huiming[6], Lin Tong[7] Zhou Shiliang[8] carried out the model test of reinforced earth retaining wall. These results showed that the wall back earth pressure shows curve distribution along with wall height. In 2009,Yang Guangqing and Zhou Yitao etc. compared the measured value with theoretical calculating value of the lateral soil pressure of reinforced earth retaining wall back and discovered that the measured value were small, and the distribution of soil pressure along with the wall height was great different from the actual measured data[9].

The effects of reinforcement was taken into consideration and the half-space theory was used to discuss the strength of reinforced earth under form of tensile failure. And then, the theory of quasi cohesive force and Coulomb were used to discuss the distribution and resultant force of wall back active earth pressure of reinforced earth retaining wall. And the calculation formula of soil pressure of reinforced earth retaining wall was proposed and tested under the condition of tensile failure.

2 Analysis of reinforced earth strength model

Assuming that the vertical layer spacing of reinforcement is h(m), thickness of reinforcement is t(m), and the tensile strength of reinforcement is RT(kN/m). The filling earth is cohesionless soil and its volume-weight is (kN/m3). Its internal friction angle is and reinforced soil interface friction coefficient is f.

Fig.1 Strength model of reinforced soil

The unit width of reinforced earth as shown in Fig.1 is taken to study the reinforced earth retaining wall. Assuming that the angle between fracture surface and horizontal direction (angle of rupture) is 45°+φ/2, the shear force which reinforcement acting on the filling earth is T(kN), and the soil weight is G=γh2cot(45°+φ/2)/2.Thereinforced earth failure can be divided into tensile failure and cohesive failure. In view of the two

3T

h

1

R

φ

452

2

h t

2

h t

t

G




- 17 -

cases, so the strength of reinforced earth was discussed from the two aspects respectively. Because the thickness of reinforcement is very small compared with its layer spacing, so the thickness of reinforcement is ignored in the following discussing.

The tensile failure is a kind of break resulted from the insufficient of tensile strength of reinforcement material when the reinforced earth arrives at its boundary state of stress.. So the shear force T which reinforcement acting on filling earth between reinforcement and earth is controlled by the tensile strength of reinforcement. That is,

TT R (1)

The relational expression under the condition of tensile failure is obtained through the force analysis about Fig.1:

3 a 1

1( )

2TR

K hh

a 1 a( 0.5 ) 2 TK h c K (2)

In the relational expression, Ka coefficient of active earth pressure, 2a tan (45 )

2K

CT is cohesion under the condition of tensile failure, tan(45 )

2 2T

T

Rc

h

。 (3)

The relational expression (2)illustrates that the cohesion of reinforced earth is stronger than the soil without reinforcement.

3 Soil pressure analysis of the reinforced earth retaining wall

3.1 Forced model based on quasi cohesive strength Assuming that when the filling earth behind reinforced earth retaining wall arrives

at the initiative ultimate equilibrium, it will slide along a certain BC plane which is enclosed by wall back, wall toe and standard plane. The sliding of ABC sliding wedge leads to the production of soil pressure on the retaining wall. There are gravel filling of 0.5m thickness behind the wall. And there is mismatch between reinforcement and gravel filling. So it can be assumed that there is no quasi cohesive strength on the interface between wall and soil. Quasi cohesive strength C is on the fracture surface and the thickness of rebar material is ignored. Considering the reinforced earth as homogeneous composite material. The force of the ABC sliding wedge are shown in Fig.2according to the Coulomb theory.

The height of reinforced earth retaining wall is H(m).Reinforcement is arranged with equal spacing h(m). The filling earth surface is standard and under the uniform loading of q0(kN/m). The friction angle of wall earth is σ (°).

Through the force equilibrium analysis of reinforced earth on the horizontal




- 18 -

direction, it can be obtained,

cot sin( )E cH R (4)

Through the force equilibrium analysis of reinforced earth on the vertical direction, it can be obtained,

20 / 2

tan cos( )tan

q H HE cH R

(5)

Fig.2 Stress diagram of the reinforced earth

Combining(4) and (5), the resultant force of lateral soil pressure on the wall back of reinforced earth retaining wall is E:

20

cos sin( ) 1 cos cos( )

tan cos( ) 2 sin cos( )E q H H cH

(6)

When the quasi cohesive strength c is 0, (6) is the Coulomb's earth pressure formula. 3.2 Soil pressure of reinforced earth retaining wall under the condition of tensile failure Setting c=cT, the resultant force E of standard soil pressure acting on the wall back of reinforced earth retaining wall under the condition of tensile failure can be obtained by (3) and (6) as following:

20

cos cos tan(45 )cos sin( ) 1 2( )tan cos( ) 2 sin cos( ) 2

TR HE q H H

h

(7)

When δ=0,and θ=45°+φ/2 in (12), it can be obtained that,

2a 0

1( )

2 T

HE K q H H R

h

(8)

When RT=0, (13) is the Coulomb active earth pressure formula. Coulomb's earth pressure theory believes that soil pressure a shows linear distribution along wall height. According to dE/dH=a and setting =0 and =45°+/2. It can be obtained that,

Cθ

2

2 tan

H

B

E

tanE

A

sin

Hc

H

0

tan

q H

R

φ




- 19 -

a a 0( ) TRK q H

h

(9)

From the (7)-(9), it can be identified that the soil pressure (resultant force) acting on the wall back of reinforced earth retaining wall under the condition of tensile failure has one more item than Coulomb's earth pressure which is related with tensile strength and vertical spacing of reinforcement. And it decreases with the increase of tensile strength and increases with the growth of vertical spacing.

Fig.3 Distribution of lateral soil pressure of reinforced retaining wall along wall

height

4 Analysis example

As shown in Fig.3, the proposed calculation method for soil pressure of reinforced earth retaining wall is compared with measured data. The parameters in references[9] areas following: the spacing between reinforcements is 0.6m when the height of wall is more than 3.2m, the spacing between reinforcements is 0.4m when the wall is shorter than 3.2m, the interface friction coefficient between the reinforcements and soil is f=0.3, the tensile strength of reinforcements is RT=6kN/m(strength values of 0.5% reinforcements strain). =19 kN/m3, =25°, q=15 kPa.

It can be seen from Fig.3 that the lateral soil pressure calculated through the tensile failure method and cohesive failure method proposed in this paper is smaller than the soil pressure which obtained by earth pressure at rest method and variable-coefficient. And the pressure is very close to the measured value. At the range of the 1/3 height from the top of the wall, the data received from the tensile failure method is smaller than measured value. At the rest of range the result is on the contrary. The measured values are enveloped in the results cohesive failure method. It illustrates that cohesive failure method is safe and reliable. And it is fit for the design of geogrid reinforced earth retaining wall.




- 20 -

5 Conclusion

Through the analysis above, the following conclusions can be received: (1) Reinforced earth cohesion under increases under the tensile failure; (2) The soil lateral pressure calculating formula proposed in this paper for the wall

back of reinforced earth retaining wall takes a full consideration of reinforcements influence on the lateral soil pressure. The result is smaller than the classical soil pressure and variable-coefficient and very close to the measured value;

(3) Soil lateral pressure of reinforced earth retaining wall increases along with the increase of reinforcement’s vertical spacing;

(4) Soil lateral pressure of reinforced earth retaining wall decreases along with the increase of reinforcement’s tensile strength.

6 References

[1] He Guangchun. Design and Construction of the Reinforced Soil. Beijing: China Communications Press, 2000.

[2] Lei Shengyou. Theory and technology of Modern Reinforced Soil. Beijing: China Communications Press, 2006.

[3] Yin Yaxiong, Pan Baotian, Wang Shengxin. Testing Study on Reinforced Earth Retaining Wall Along Yang Quan-Shexian Railway. Chinese Journal of Rock Mechanics Engineering,2003,22(Supp.2): 2816-2919.

[4] Wang Xiang, Xu Lin rong. Test and analysis of two-step retaining wall reinforced by geogrid. Chinese Journal of Geotechnical Engineering, 2003, 25(2): 20-24.

[5] Yang Guang-qing, Lv Peng, Pang Wei, et al. Research on geogrid reinforced soil retaining wall with wrapped face by in-situ tests .Rock and Soil Mechanics, 2008, 29(2): 517-522.

[6] Tang Huiming, Lin Tong. Centrifuge modeling test on reinforced earth wall at wushan county in reservoir area of three gorges project .Chinese Journal of Rock Mechanics Engineering, 2004, 23(17): 2893-2901.

[7] Lin Tong. Study on the application of centrifuge modeling test tosuper2elevation reinforced earth retaining wall . china civil engineering journal, 2004, 37(2): 43-46.

[8] Zhou Shi-liang, He Guang-chun, Wang Cheng-zhi1 et al. Study on stepped reinforced soil retaining walls by model tests. Chinese Journal of Geotechnical Engineering,2007, 29(1): 152-156.

[9] Yang Guang-qing, Zhou Yi-tao, Zhou Qiao-yong, et al. Experimental research on geogrid reinforced earth retaining wall. Rock and Soil Mechanics,2009, 30(1): 206-210.

[10] China Communications 2nd Highway Survey Design and Research Institute. Specifications for Design of Highway Subgrades (JTG D30-2004).Beijing: China




- 21 -

Communications Press, 2004: 44-45.




22

Mechanical Analysis of Flexible Base Durable Asphalt Pavement Structure

SONG Yang1,2, SUN Wen-jun1,2*, ZHU Xiao-yun4, ZHANG Hai-feng2,3

1. Hebei Engineering and Technical College, Cangzhou, Hebei, 061001, China

2. College of Civil Engineering, Hebei University of Technology, Tianjin 300401, China

3. HuaBei Expressway Co., Ltd, Beijing, 100176, China

4. Tianjin transportation vocational college, Tianjin, 300110, China

Abstract: In order to provide basis for the design of flexible base durable asphalt pavement

structure. The influence of all kinds of parameter combination on different control indicators

was analyzed by combining the extremum of each structure-layer parameters, such as

different asphalt aggregate thickness, different layer thickness under the same total thickness,

and different elasticity modulus. Regression analysis was carried out based on the data in

database by the using of Minitabdata analysis software. The mechanical response model was

obtained. And the influence that each structure-layer parameters acting on the mechanics

index of pavement structure were measured. The research shows that the total thickness of

asphalt layer is the key influence parameter of tensile strain indicator of asphalt layer bottom.

The flexible base layer thickness is the main influence parameters of top soil base

compression strain index. The flexible subbase modulus parameter has influence on every

index obviously. Soil base modulus is the main influence parameter of surfacing deflection

and the top soil base compressive strain index.

Key words: flexible base; durable pavement; asphalt layer bottom tensile stress; top soil base

compression strain; mechanical response model

1.Introduction In recent years, in order to adapt to the growth of traffic volume and reduce the

road maintenance and traffic delays caused by road maintenance. The concept of "durable asphalt pavement" [1] was put forward in Europe and America. The idea is that the working life of road will be 40 to 50 years. And there is no structural damage in the period of using. Functional maintenance of the surface layer needs to be carried out every 10 to 15 years. Flexible base has good high-temperature stability, anti-fatigue cracking, and good water stability. And it can greatly reduce stress intensity factor of crack at the bottom of the surface. And it can prevent the production of reflection crack effectively [2], etc. This kind of pavement structure has some features such as long service life, small harm in the early time, convenient maintenance and small influence on traffic.

◆Research Paper◆




23

The durable asphalt pavement has become a hot focus in the academic circles [3-4]. Shu Fumin [5] and other scholar analyzed the mechanics index of the asphalt pavement structure through orthogonal experiments. Sun Hongyan et al. [6] carried out the sensitivity analysis of structure-layer parameters of durable asphalt pavement through digital simulation. And there is a number of scholars have studied the index of durable asphalt pavement [7] and compared the characteristics of durable asphalt pavement in China with foreign countries to provide a reference for the follow-up study. But the related research of flexible base durable asphalt pavement is still relatively few.

In this paper, a set of various composite data of different structure layer thickness and modulus is established. The influence of different structure-layer parameters of flexible base durable asphalt pavement on different control indices is analyzed, and the mechanical response model is deduced. That can be used to rapidly design durable asphalt pavement with different demand. Composite data includes the information of structure and material, deflection shape of surface of pavement and various key strain data, which provides a reference for optimizing the design of pavement structure, in future study.

2. Analysis of the influence of the pavement structure layer parameters on the control indices 2.1 Structure parameters of durable asphalt pavement’s determination

Working condition of durable asphalt pavement structure is simulated by using the ANSYS finite element analysis software. Because of the high cost of the flexible base in the initial stage, the flexible base durable asphalt pavement structure is less applied in China. Control indices which are suitable for flexible base durable asphalt pavement structure’s design in China is proposed according to some existing data [8, 9], such as, the bottom of the asphalt layer strain tensile should not be more than 120με, the top of the soil base compressive strain should not be more than 280με, surfacing deflection should be less than 35 (0.01mm). In pavement structure design, if these three indicators can be satisfied, it is called durable asphalt pavement. Suppose that the form of flexible base durable asphalt pavement structure is 3~7cm SMA-13/AC-13+6~22cm SMA-16(20)/AC-20+8~16cm ATB-25+15~55cm graded broken stone. A kind of pavement structure parameters is designated according to

'Code for design of highway asphalt pavement', as shown in Figure 1 and Table 1. Flexible base asphalt pavement consists of five layers, namely SMA-13/AC-13,

SMA-13/AC-13, ATB-25, graded crushed stone and soil matrix. Each layer with three basic parameters which are thickness, elastic modulus and

Poisson's ratio. Calculation data can be determined in the range of other structural parameters, by

controlling the total thickness of asphalt layer. And then, the influences of each structure layer can be determined.




24

Table 1 parameters of flexible base asphalt pavement structure

Material Thickness Elasticity Modulus /Mpa Poisson's ratio

SMA-13/AC-13 3~7cm 1600~2000 0.35

SMA-13/AC-13 6~22cm 1600~4000 0.35

ATB-25 8~16cm 1200~1600 0.35

graded broken stone 15~55cm 0.35

soil matrix -- 35~75 0.4

Figure 1 Schematic diagram of finite element model

The specific data setting includes: asphalt layer total thickness is 17cm to 45cm, the selected thickness for analyzing is 17cm, 19cm, 21cm, 23cm, 25cm, 27cm, 29cm, 31cm, 33cm, 35cm, 37cm, 39cm, 41cm, 43cm and 45cm.Within the same thickness, different thickness constitution of SMA-13/AC-13,SMA-13/AC-13andATB-25 is adjusted. The maximum and minimum in the range of each structure-layer parameter are combined. The parameter combination is shown in Table 2. 2.2Analysis of the influence of the total thickness of asphalt layer on the design index

In order to compare the influence of different asphalt layer thickness on each control index, according to the 'Code for design of highway asphalt pavement' [6] and actual road construction experience, this paper chooses15 types of asphalt layer thickness in the range of 17cm to 45cm.Surfacing deflection, tensile strain values of asphalt layer bottom and compressive strain values of top soil base are calculated respectively in this paper, according to different structural parameter combination. The results are shown in figure 2 to figure 4.

Table 2 Structure parameter combination table




25

NO. Thickness of

graded

crushed

stone

Upper

modulus

Middle

modulus

Lower

modulus

K1 K2 soil base

modulus

1 15 1600 1600 1200 20 0.45 35

2 15 1600 1600 1600 60 0.65 75

3 15 2000 4000 1200 20 0.65 75

4 15 2000 4000 1600 60 0.45 35

5 55 1600 4000 1200 60 0.45 75

6 55 1600 4000 1600 20 0.65 35

7 55 2000 1600 1200 60 0.65 35

8 55 2000 1600 1600 20 0.45 75

Figure 2 Effect of asphalt layer total thickness to surfacing deflection By Figure 2, when the total thickness of asphalt layer is less than 23cm the

pavement structure’s pavement deflection is greater than the critical deflection value(35(0.01mm)) of asphalt pavement, which can not meet the requirement of durable asphalt pavement. When the total thickness of asphalt layer is greater than 41cm, the pavement structure’s pavement deflection is smaller than the critical deflection value of asphalt pavement,, which can meet the requirement of durable asphalt pavement. When the thickness of asphalt layer is between 41cm to 23cm ,whether the indexes of structure pavement surface deflection will meet the requirements of durable asphalt pavement structure is related to the material parameters of pavement,.

As shown in figure 3,the value of tension strain at base of asphalt layer is smaller than the value of critical tension strain at base of durable asphalt pavement layer by 120με, when the total thickness of asphalt layer is less than 25cm, which can not meet




26

the requirement of durable asphalt pavement. Most tensile strain values of asphalt layer bottom of pavement structure combination meet the requirement of durable asphalt pavement, when the total thickness of asphalt layer is greater than 43cm.whether The index of tension strain at base of asphalt layer will meet the requirements of durable asphalt pavement structure is related to the material parameters of pavement, when the thickness of asphalt layer is between 25cm to 43cm.

Figure 3 Effect of asphalt layer total thickness on asphalt layer bottom tensile strain value

Figure 4 Effect of asphalt layer total thickness on top soil base compressive strain values

As shown in figure 4, most top soil base compressive strain values of pavement structure are greater than critical value (280με), when the total thickness of asphalt layer is less than 23cm, which cannot meet the requirement of durable asphalt




27

pavement. Most top soil base compressive strain values of pavement structure is smaller than critical value (280με),when the total thickness of asphalt layer is greater than 43cm, which can meet the requirement of durable asphalt pavement. Whether The index of top soil base compressive strain will meet the requirements of durable asphalt pavement structure is related to the material parameters of pavement structure, when the total thickness of asphalt layer is between 23cm to 43cm.

Synthesizing above figures, it can be seen that, in general, surface deflection and top soil base compressive strain will satisfy the requirement of durable asphalt pavement, if the tensile strain values of asphalt layer bottom of asphalt pavement structures is smaller than critical value. In the range of selected control indices and structure parameters, pavement structure hardly meet the requirement of durable asphalt pavement, when the total thickness of asphalt layer is smaller than 23cm.Most index value of mechanical response are smaller than critical value, which can be thought as durable pavement, when the total thickness of asphalt layer is greater than or equal to 43cm.durable asphalt pavement structure can be achieved through designing the thickness and material modulus of each layer, when the thickness of asphalt layer is between 23cm and 43cm.

2.3Analysis the influence of flexible subbase parameters on control indexes In order to compare the influence of flexible subbase’s thickness on each control

index, according to the 《Code for design of highway asphalt pavement》and actual road construction experience,10 kinds of flexible subbase’s thickness in the range of 15cm to 60cm are selected in this paper. Surfacing deflection, tensile strain values of asphalt layer bottom and compressive strain values of top soil base are calculated respectively in this paper. The results are shown in figure 5.

Figure 5 Relationship of flexible subbase’s thickness and each index value It can be seen from the above figure, surfacing deflection is smaller than limit

deflection value (35(0.01mm)), when the flexible subbase’s thickness is greater than 43cm;Values of tensile strain of asphalt layer bottom is smaller than limit bottom




28

tensile strain values (120με), when the flexible subbase’s thickness is greater than 31cm; Top soil base compressive strain is smaller than critical value (280με), when the flexible subbase’s thickness is greater than 29cm;

Compressive strain of top soil base is greatly influenced by the change of flexible subbase’s thickness. Along with the increase of thickness of flexible base layer Surfacing deflection, tension strain at base of asphalt layer and top soil base compressive strain values decrease gradually and the rate of decrease gradually reduce. The thickness of flexible subbase should be controlled within the range of 50cm, considering the mechanical property of pavement structure, construction cost and other factors.

In order to compare the influence of different flexible subbase’s modulus on each control index, Different groups, K1 and K2 are selected. Surfacing deflection, tensile strain values of asphalt layer bottom and compressive strain values of top soil base are calculated respectively in this paper. The results are shown in table 3.

Table 3 Calculated index value based on K1 and K2 mechanics

index K2 K1 20 30 40 50 60

0.45 44.97 42.42 40.22 38.45 37.01

0.50 43.88 41.04 38.77 36.99 35.54

0.55 42.78 39.64 37.31 35.5 33.99

0.60 41.4 38.14 35.8 33.94 32.47

Surfacing

deflection(0.

01mm)

0.65 39.98 36.64 34.22 32.4 30.95

0.45 161.3 146.6 132.5 120.5 110.4

0.50 155.3 137.9 122.7 110.2 99.67

0.55 148.8 128.7 112.4 99.42 88.27

0.60 140.2 118.4 101.6 87.89 76.92

tension

strain at

base of

asphalt

layer(×10-6) 0.65 131 107.7 90 76.41 65.55

0.45 269.1 267.0 258.8 248.5 238.3

0.50 269.3 262.5 250.6 238.1 226.3

0.55 267.8 255.8 240.5 226.0 212.5

0.60 263.9 246.5 228.6 212.1 198.1

Top soil

base

compressive

strain(×10-6) 0.65 257.6 235.4 214.7 197.4 183.0

According to the table above, index values reduced in different degree along with

the increase of dynamic modulus parameters by calculating the effect of dynamic modulus parameters K1 and K2of different flexible subbaseon each index. K1 and K2 should be increased combining with the pavement structure to improve the durability of asphalt pavement.




29

3 mechanical response model of flexible base durable asphalt pavement structure’s parameters

On the one hand, asphalt pavement structure should meet the mechanical durability standards, on the other hand, asphalt pavement structure should achieve there requirement of economic. Therefore, it is needed to meet the requirements of the structural layer material parameters and thickness.

The regression analysis was conducted for the data in the database which was established according to the above calculation by using the Minitab data analysis software. And the effect of the structure layer material parameters on the mechanics index of pavement structure is analyzed.

Because the thickness and modulus of the upper surface course have little effect on each calculation index, it is not considered in the regression analysis. The regression formula used 235 groups of data, the specific conclusions are as follows. Surface deflection:

ln 6.40 0.259ln 2 0.216ln 3 0.232ln 4 0.0707 ln 2

0.300ln 3 0.176ln 1 0.457 ln 2 0.495ln 4

l H H H E

E K K E

(1)

=0.0854264S - 93.0%qR S - 92.8%qR S （adjusted）

tensile strain of Asphalt layer bottom:

ln 7.69 0.478ln 2 0.328ln 3 0.210ln 4 0.0064ln 2

0.155ln 3 0.486ln 1 1.21ln 2 0.0734ln 4t H H H E

E K K E

(2)


soil base top compressive strain:

ln 10.8 0.497 ln 2 0.402ln 3 0.612ln 4 0.0372ln 2

0.183ln 3 0.231ln 1 0.488ln 2 0.362ln 4c H H H E

E K K E

(3)


In the formula: l—surface deflection (0.01mm)；

t —Asphalt layer bottom tensile strain values (με)；

c —soil base top compressive strain values (με)；

S —Standard deviation of regression model’s error




30

q-R S —The percentage of the regression model error accounting for the total

errors. Values between 0% and 100%. The greater the value, the better regression model is agree with the data.

q-R S（adjusted）—The value of adjustive q-R S are between 0% and 100%. The

more R-Sq(adjust)close to R-Sq, the more reliable the regression model is.

q-R S The larger the value, the better. Latter q-R S is after the adjustment value by

Minitab. There is an association, If the value bigger than 70%.If the value bigger than 85%, there relationship is significant. The reliability of regression formula was tested by using 200 groups of data which

are not used in the regression calculation. Compared with the results calculated bt the regression formula, the correlation coefficient is 0.9681.Therefore, the relevancy of regression formula is high, and the deviation is small.

According to the regression formula, the influence of asphalt layer modulus on each index value is smaller than the thickness on each index value. Therefore, the key point of the design of durable asphalt pavement structure’s is determining the laminate construction thickness.

4 Summary

The typical flexible base durable asphalt pavement structure is selected in this paper. And computational analysis of mechanical response of structural layer parameters, surface deflection, asphalt layer bottom tensile strain and soil base top compressive strain was conducted. The mechanical response model of parameters of flexible base durable asphalt pavement structure is proposed. The conclusions are as follows:

(1) The total thickness of asphalt layer is the main influence parameter of asphalt layer bottom tensile strain indicator. The durability of pavement structure can be achieved by designing and adjusting the thickness of each structure layer and material modulus can realized, when the thickness of asphalt layer is between 27cm to 43cm.

(2) The flexible base layer thickness is the main influence parameter of top soil base compression strain index. The flexible subbase modulus parameter has obvious influence on each index. Therefore, the dynamical modulus of the flexible subbase should be increased to improve the durability of pavement structure.

(3) Soil base modulus is the main influence parameter of surfacing deflection and the top soil base compressive strain index. With the increase of soil base modulus the Surfacing deflection and soil base top compressive strain show a decreasing trend.

(4)Examined by formula, the Mechanical response models of each design indexes was remarkable, which were obtained by the regression using the Minitab data analysis software.




31

5. Acknowledgements This paper is supported by the Research Foundation of Education Bureau of He

Bei Province(QN2015036), Water resources research and extension project of Hebei Province(2015049). The first author: Song Yang, male, born in 1982, Dr. of road engineering, lecturer. Corresponding author: Sun Wen-jun, male, born in 1982, a master degree of Rock and soil mechanics, lecturer. 6 References [1]Chen Xiao-ting, Sun Li-jun, Li Feng. Structural Characters of Perpetual Asphalt

Concrete Pavements and Design. Highway, 2005, 8: 239-242. [2] Yin Wei, Wang Lei, Zhang Dong. Multi factor analysis of structure design of long

life asphalt pavement, 2011, 2: 70-75. [3] Xu Ouming, Han Sen. Method for determining the thickness of long life asphalt

pavement in South Korea . Chinese and foreign highway,2006,(2):79-82. [4] Li Tieshan. Feasibility analysis of improving the service life of Asphalt Concrete

Pavement. Highway, 2013, 10: 44-47. [5] Shu Fumin, Qian Zhendong, Tang Jianjuan. Orthogonal analysis of the structural

mechanics index of the new long life asphalt pavement .Shanghai highway, 2007, 3: 19-22

[6]Sun Hong-yan, Zheng Chuan-chao. Sensitivity Analysis of Strains and Stresses for Long-life Asphalt Pavement .Journal of Zhengzhou University (Engineering Science), 2010, 4: 27-30.

[7]Nie Yi-hua, Zhang Qi-sen. Researches on Bending Index of Full-depth Asphalt Pavement Structure. Journal of Highway and Transportation Research and Development, 2007, 2: 5-7.

[8]Cui Peng, Shao Min-hua, Sun Li-jun. Research on design indices of perpetual asphalt pavement. Journal of Traffic and Transportation Engineering, 2008, 3: 37-42.

[9] Ping Shu-jiang, Shen Ai-qin1, Li Peng. Study of Fatigue Limit of Asphalt Mixture for Perpetual Pavement. China Journal of Highway and Transport, 2009, 1: 34-38.

ISSN:2372-0743 print

ISSN:2373-2989 on lineInternational Journal of Ground Sediment & Water

Vol. 02

2015

Journal Website: http://ijgsw.comze.com/

You can submit your paper to email: [email protected]

- 32 -

Erosion and Sediment Yield Time-Space

Distribution Characteristics Research of

Slope-Gully System Based On Simulated

Rainfall

Fan Dong-ming1,Yang Chun-xia

2,Wu Qing

1,Wang Jia-xin

1,Yang Ji-shan

2

1. North China University of Water Resources and Electric Power. Department of Resource and Environment, Zhengzhou, 450045, China,2. Institute of Yellow River Hydraulic Research, Key Laboratory of Yellow River Sediment Research of Ministry of Water Resources, Zhengzhou,450003,China

Abstract Using the automatic artificial rainfall system of MWR loess plateau soil and water

loss process and control key laboratory, the researchers did simulation experiments of three

different rainfall intensity to artificial simulation bare slope gully system, and analyzed

erosion and sediment yield time-space distribution characteristics of slope-gully system.

Results indicate that: erosion and sediment yield process of slope-gully system with the

increase of rainfall duration showed a trend of increased volatility; the middle of gully slope

and transition region of slope-gully system developed earlier and fastest-growing; ditch slope

sediment yield and ditch slope runoff sediment concentration have the largest contribution to

the export of slope-gully system runoff sediment concentration; in slope-gully system,

lower-middle part and slope-ditch slope transition area are erosion prone areas; which shows

that it is effective to control the erosion and sediment yield of loess plateau slope gully unit by

adopting stress governance ditch and also measures of slope setting in practice.

Keywords: Slope-Gully System; Erosion and Sediment Yield; Runoff Sediment

Concentration; Time-Space Distribution Characteristics

1 IntroductionSoil erosion has become a threat to modern society and sustainable agricultural

development of global environmental problems, it can not only lead to the continued

degradation of land quality, but also it is the main source of non-point source

pollutants of water resources [1]

.Slope-gully system is the basic component unit of the

loess plateau watershed and control soil and water loss, the basic management unit of

the restoration and reconstruction of ecological environment, is the leading source of

small watershed erosion and sediment yield at the same time. The erosion

phenomenon and law of exploration, can provide slope gully optimized configuration

Research Paper



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of soil and water conservation measures with scientific basis, for rehabilitation and

reconstruction of ecological environment is of great significance [2]

. Therefore, the

slope-gully system in the Loess Plateau soil erosion has always been much attention

and research experts.

In terms of runoff and sediment yield in the slope gully system, many scholars on

the Loess Plateau sediment yield process studies carried out in different time-space

scales [3-6]

; The observation results Juying Jiao, etc show that the sheep ditch

watershed in Shanxi between watershed gully slope accept to runoff erosion and

sediment yield is 1.8 times that of the slope does not accept gap between runoff [7]

;

Based on the model of concept of self-organization by Jinren Ni, the development

process of slope is simulated and the relationship between sheet erosion and rill

erosion in slope erosion is analyzed. The influence of slope on the speed of the

development of slope is also discussed[8]

;Peiqing Xiao used indoor artificial rainfall

experiment method to study the influence of the evolution of the slope erosion on the

sediment yield of the erosion and analyzed the contribution of different stages of gully

erosion to the sediment yield of slope erosion[9]

.However, the study on the temporal

and spatial characteristics of the vertical change of soil erosion and sediment yield is

less, and the research results have a certain reference value for the identification of the

erosion and development of slope gully system.

1 Materials and Methods

1.1 The slope-gully system model The slope-gully system model is variable slope movable steel soil groove with 10m

length and 1m wide.The device was composited with slope and gully, filled with

Zhengzhou Mangshan loess and the slope and gully gradient respectively was 20° and

35°. According to the observation and analysis,the slope-gully system were broken up

into one to ten(shown in Figure 1).

1.2 Experimental Design Simulated with the typical rainfall which occurred on the Loess Plateau, Select the

rainfall intensity was 66mm/h, 85mm/h and 120mm/h.Based on the basic stability of

erosion, the rainfall lasted for 98min,60min and 56min. Before the test, the soil had

been 5mm sieve, then layered filling and compaction. The filling thickness of each

layer is 10cm, and the total filling thickness is 45cm and to control the density in the

range of 1.20-1.25g/cm3.

2 Experimental observation

During the experiment, muddy water samples was got every 2min, and including

to extract the samples from different spatial positions with 100ml syringes, Take the



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method of water and sediment density conversion to calculate the runoff and sediment

yield and other parameters At the same time,recording the surface erosion evolution

by photographed every 2-4min .

Figure 1 slope-gully system model and rainfall simulation system diagram

3 Results and analysis 3.1 Runoff and Sediment Yield Process Analysis

It is very important to study the dynamic changes of soil erosion and sediment

yield in the study of the mechanism of erosion and sediment yield in the Loess Plateau.

From experimental data, the sediment yield process curve of each rainfall was shown

in Figure 2. The erosion sediment yield of slope gully system in different rainfall

intensity increased with the increase of the rainfall time. As can be seen from the chart,

the erosion sediment yield of slope gully system in different rainfall intensity was

increased with the rainfall time goes on. Sediment yield process line of the rainfall

intensity of 66mm/h is the lowest. With the increase of rainfall, sediment yield

process have experienced 3 stages of “increase - volatility stable - Increase” phase.

The first phase of the increase occurred within 30 minutes, the volatility stable phase

occurred probably between 30 and 60 minutes, and the last increase phase occurred

after 60 minutes later. The sediment yield process line of 85mm/h is as consistent as

the line of the rainfall intensity of 120mm/h. In the pre 16min of rainfall, the sediment

process line of 120mm/h is significantly higher than that of 85mm/h. Because rainfall

at the beginning stage, the heavy rainfall that with greater energy and erosion force of

raindrop splash erosion and surface erosion on the slope, leading to rainfall erosion

and runoff sediment transport capacity increased. After 20min, rainfall runoff and

sediment process line of 85mm/h and 120mm/h is no longer obvious, which shows

that the surface erosion and development of slope gully system once started, more

35

20

7

8

9

6

10

5

1

43

2

Slope-gully

edge line Slope

Gully



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than 85mm/h above the rainfall can lead to strong soil erosion.

Figure 2 sediment yield process

3.2 Temporal distribution characteristics of sediment yield of slope-gully system The total sediment yield of slope gully system is 65kg.In order to facilitate the

analysis and comparison, the 66 mm/h rainfall simulation experiment eventually

sediment yield as a reference, selected the stage of equivalent sediment under three

kinds of rainfall intensity, and according to a period of 10min, the sediment yield in

each period for the proportion of the total sediment can be count. It was shown in

Figure 3.

When the sediment yield of 3 kinds of rain intensity reached about 65kg, the

rainfall of 66mm/h had experienced 98min, while the 85mm/h and 120mm/h of

rainfall only experienced 60min and 56min respectively. This indicates the rainfall

more than 85mm/h has an acute process of sediment yield. From Figure 3, rainfall of

66mm/h sediment yield curve is relatively flat, while the 85mm/h and 120mmh

rainfall runoff increased significantly with the increase of rainfall stage. Especially,

the heavy rainfall intensity of 120mm/h, the slope gully system in the first rainfall

period has occurred severe erosion and sediment yield. Followed by the 85mm/h

rainfall, in the second, third rainfall stages, the proportion of the erosion sediment

yield increased rapidly, and then the sediment yield ratio is close to that of 120mm/h.

It is showed that for bare slope gully system, the erosion caused by rainfall of 85mm/

h or more has been very intense, especially the high intensity rainfall of rainfall

duration exceeds 30min.

3.3 Spatial distribution of sediment content of slope gully system Sediment content of export runoff of slope gully system is the comprehensive

response runoff sediment of slope and gully, combined with runoff sediment content

spatial distribution characteristics of slope-gully system, can be reacted spatial

distribution characteristics of erosion and sediment yield intuitively.



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Figure 3 Distribution characteristics of sediment yield in each stage of rainfall

Six periods of rainfall distribution include sediment content of slope gully

system(Sp-g), runoff sediment of slope(Sp) and runoff sediment of gully(Sg) in three

kinds of rainfall intensity, which shown in Figure 4. Along with the rainfall duration

increasing, the runoff sediment concentration tended to increase, especially for

85mm/h and 120mm/h rainfall is more obvious; The runoff sediment content of slope

gully system is between runoff sediment content of slope and that of gully, Sp and Sg

are analyzed for further regression(Table 1), it was found that under 85mm/h and

120mm/h rainfall intensity conditions, the relationship of runoff sediment

concentration of slope gully system, Sp and Sg showed a positive correlation

relationship. At 66mm/h rain intensity conditions, Sp-g and Sg was positively

correlated, and negatively correlated with Sp. Further analysis of Sg and Sp coefficients

are found, gully sediment concentration degree of effect on the slope-gully system

runoff sediment concentration is stronger than the extent of slope runoff sediment

concentration. As at 66mm/h rain intensity conditions, coefficient ratio of Sg and Sp is

1.36: 1,and in 85mm / h and 120mm / h rainfall intensity, coefficient ratios of Sg and

Sp is 3.18: 1 and 29.35: 1, and it indicates that the greater the rainfall intensity, slope

sediment runoff of slope gully system on export sediment increase stronger. Therefore,

controlling runoff sediment concentration, taking into account the need to reduce the

slope and gully runoff sediment concentration, especially in parts of the gully runoff

sediment concentration.



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Table 1 The relationship of sediment concentration between slope or gully and the

whole system

The relationship of sediment concentration

between the whole system(Sp-g) and

gully(Sg) slope(Sp)

Coefficient

of Sg

Coefficient

of Sp

correlation

coefficient

R

66mm/h Sp-g=0.7873 Sg -0.5802 Sp 0.7060 -0.5802 R=0.9984

85mm/h Sp-g=0.7060 Sg +0.2222 Sp 0.7060 0.2222 R=0.9912

120mm/h Sp-g=0.8305 Sg +0.0283 Sp 0.8305 0.0283 R=0.9940

Figure 4 Spatial distribution of runoff sediment content of slope and gully

3.4 Spatial and temporal distribution of sediment concentration along the slope and gully

With the rainfall, runoff sediment concentration of each section also showed a trend

of increased volatility, especially to gully part and the lower part of the slope is the

most obvious. For 66 mm/h, with the extension of rainfall, the slope gully system

development to the bottom of the slope section 5,while for 85mm/h and 120mm/h,

erosion ditch in the slope gully transition zone developed to the 2 and 3 section of the

slope in the middle of the slope. The rainfall of 85mm/h and 120mm/h on the surface

morphology of the slope gully system is more serious. In the middle of the slope gully

system and the transition zone of the slope gully system is the erosion prone region. It

was shown in Figure 5.



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Figure 5 Temporal and spatial distribution of sediment content

4 ConclusionsBased on the rainfall simulation of the slope-gully system under the rainfall



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intensity of 66mm/h, 85mm/h and 120mm/h conditions, Gotten the following

conclusions:

(1) The high intensity rainfall has a strong destructiveness to the bare slope gully

system, especially the rainfall duration is more than 30min of the strong rainfall

(2) In slope-gully system, the contribution of gully slope sediment and runoff

sediment on the outlet runoff of slope gully system is maximum. Thus, should be a

focus to reduce runoff sediment concentration on gully site when controlling runoff

sediment concentration.

(3) In the lower part and the transitional zone of slope-gully system are prone to

erosion area. In practice, the synthetical protection engineering and vegetation

measures may be considered.

According to the results of this experiment, it is shown that in practice, the

reasonable configuration of the slope treatment is adopted , which can effectively

control the soil and water erosion in the Loess Plateau.

5 Acknowledgement

This research was supported by the central level scientific research institutes for

basic R&D special business(No.HKY-JBYW-2014-08).

6 Reference

[1] Lei TW, Zhang QW, Yan LJ, etal. A rational method for estimating erodibility and

critical shear stress of an eroding rill. Geoderma, 2008, 144: 628-633.

[2] XiaoPei-qing, Zheng Fenli, Yao Wenyi. Research Progress on Relationship of

Sediment Yield and Erosion Mechanism Between Hill Slope and Gully Slope

System. Research of Soil and Water Conservation,2004, 11(4):101-104.

[3] He Jijun,Gong Huili,Li Xiaojuan. Effects of rill development on runoff and

sediment yielding processes. Advances in Water Science ,2014,25(1):90-97.

[4] Liu Junti, Sun Liying, Zhang Xuepei, A Study of Rill Evolution Process and

Sediment Yield Characteristics on Loess Slope. Bulletin of Soil and Water

Conservation, 2013,33(3):18-23.

[5] Ding Wenfeng , Li Mian, Zhang Pingcang , et al. Experimental study on the

sediment yield characteristics in slope-gully system . Transactions of the Csae,

2006, 22(3):10-14.

[6] Wang Wen-long, Lei A-lin, Li Zhan-bin, Spatial distribution of runoff and

sediment in the vertical belts of soil erosion chain in loess region of hilly and gully.

Advances in Water Science, 2004,15(1):24-28.

[7] Jiao Juying, Liu Yuanbao, TangKeli.An Approach to Runoff and Sediment

Generation of Gully and Intergully Land in Small Watershed. Journal of Soil and



Vol. 02

2015



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Water Conservation, 1992,6(2):24-28.

[8] Ni Jinren, Han Peng, Zhang Jian. Characteristics of loess slope evolution based on

concept of self-organization. Shui Xue Bao, 2002(1):6-9.

[9] Xiao Peiqing, Zheng Fenli,Wang Xiaoyong. Experimental Study on Erosion

Pattern Evolvement and Sediment Process on Loessal Hillslopes. Journal of Soil

and Water Conservation,2008,22(1):24-27.



Vol. 02

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Simplify the Structure of The Surface

Mining and Analytic Calculation

Zhang Mei1, Meng Da

2

1.Agricultural University of Hebei, College of Urban and Rural Construction, Baoding, 071000, China 2.China Academy of Building Research, Beijing,100190, China

Abstract: Based on the NATM, established the mechanical model of the mining surface

structures, researched the forming of the non-hinged arch during the coal seam mining. Using

elasticity center method calculated the internal forces of the non-hinged arch, got the strength,

rigidity and stability of the surrounding rock and supporting structure. With analytic

calculation, Analyzed the rock stress evolution of the adjacent coal seam mining and the stress

distribution of the stope roof rock evolution. Based on the stress field evolution of the stope,

analyzed the force and the crack development in different regions of the rock mass, studied

the distribution of the strain and shear stress in the rock mass and the impaction of mining

velocity on rock stress distribution. Verified the rationality of the surface structure of the

model adopted in this paper.

Keywords: mining face structure; mechanical model; no hinged arch; adjacent coal seam;

elasticity center method

In the traditional surrounding rock of roadway control theory, the surrounding

rock of roadway is a loading, should use the thick concrete to support the loosen rock

mass. New Austrian Tunneling Method (NATM) considered rock is a carrier

mechanism, build a supporting structure that is thin-walled, flexible and closed to the

rock mass, to bear the pressure and maintain maximum stability of the rock mass

without loosen or damage. NATM was introduced to China in 60’s; it was developed

rapidly in late 70’s and early 80’s. Now NATM is used in all major and difficult

underground works, it almost became a basic method in soft crushing rock

location to build tunnel.

Based on the NATM, the paper established the mechanical structure model of the

roadway mining face structures in the mining process. For the statically indeterminate

structure using the force method, the matrix displacement method and moment

distribution method to calculate the internal forces, got the strength, rigidity and

stability of the surrounding rock and the support structure.

1 Mechanical model During the coal mining, the advancing of working face keep the internal stress of

coal rock continuously self-adjustment, resulting the internal stresses uneven in coal

Research Paper



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rock, automatically formed an arch structure in rock. The rock in the arch structure

located in a region of high stress concentration, the rock on the inside of the pressure

arch and near the side of the mined-out area, due to the unloading, the stress is

reduced, be in the unloading state. The rock stress near the coal mining gathered to the

goaf and gradually increasing. When coal mining to a certain distance, the stress is

greater than the ultimate strength of the rock, the coal seam roof will have the first

fracture, collapse and caving, also known as the first weighting. The rock mass

structure can be simplified show as figure 1. The structure in first weighting bearing

the concentration stress q1 caused by the coal mining, upper strata and their own

gravity q2, the caving rock inside the structure generated extrusion pressure q3 and q4,

along with unloading the lower strata produced the buoyancy q5 and concentrated

stress q6, extrusion pressure q7 and q8 of the surrounding rock . Along with coal

mining continue, the stress arch continue adjustment, when the elasticity modulus of

top slab strata is larger, the situation shown in figure 2 will appear, that plus a box

structure by an arch structure. Because the top roof has a high ultimate strength, it can

bear the additional stress generated by gravity and stress concentration came from the

surrounding rock. The arch internal caving rock will provide some support to the arch

structure, and will form one pillar at the junction of arch and box interface. Due to the

loose structure of the caving rock, with more flexibility and lower compression

modulus, can not be simplified into a hinge support, but it can be simplified into the

spring holder.

Fig.1 The stress arch and load distribution of first weighting

With the increasing of advance distance, when the structure internal forces is

greater than the ultimate strength of the hard layer, the coal layer will collapse again,

formed the structure shown in figure 3. Two small arches are connected, and he

connection point is connected to the base plate used a spring holder. In this stress arch

adjust process, there will be consolidation phenomenon. When the mining to a certain

distance, two small arches will merge into a large arch, shown as figure 4. Later

keeping repeated the above process to produce small arches, and finally merged into a

larger arch structure. In this process, the arch structure forces continue to make



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adjustment, but the kind of force suffered has not changed, shown as figure 5-6.

Fig.2 The stress arch and load distribution before second weighting

Fig.3 The critical stress arch and load distribution before second weighting

Fig.4 Small arch mergers and loading distribution map

After completed to advance the mining work face, there is a long time to form

stable large arch as shown in figure 7. But because after a long period standing, the

surround structure no longer bear the concentration stress. The evolution of these arch

structures also reflected the transfer direction of the rock stress indirectly. It should be

noted that the arch of the pressure arch structure within roof and floor of the coal

seam is asymmetric. Mainly due to the own weight of the top slab, the range of rock

caving and arch high are both large, the caved rock layer will compact the bottom slab,



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it will suppress stretching downward of the arch structure in the bottom slab, the

arch height smaller.

Fig.5 Multi-arch and loading distribution map

Fig.6 Stress arch merge gradually loading distribution map

Fig.7 Final stable arch and loading distribution map

2 Engineering Applications 2.1 Project Overview

The working face 22201 is the first face of North 2 mining area 2# Coal of a

mine, using leaving road along the goaf and Y-type ventilation. The geological

structure is relatively simple, the overall structure is monoclinic, the average

inclination 4 °, the average coal thickness 2m, the face is mainly coking coal and high

gas content, gas pressure 2MPa. Its northern formed 22202 face, the remaining 2 #



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coal was not explored. In the nether 3+4# Coal face, only the mining 24208 Face in

southern, other position both no working, and 3+4# coal average thickness 4m. The

5# coal is under the 2# coal, distance 20m, coal thickness 4m. The 22201 Face is the

two-roadway plus one borrow roadway layout mode, when the working face stoping,

the machines rail combination roadway and assist roadway are inlet air roadway, the

22202 Track way is the main return airway of 22201 mechanized mining face. Rock

mechanics parameters calculated as table 1.

Tab.1 Calculation rock mechanics parameters

Litholo

gy

Thi

ckn

ess

m

The bulk

modulus

GPa

The shear

modulus

GPa

Density

kg/cm3

Friction

angle°

Internal

Cohesio

n

MPa

Tensile

strengt

h

MPa

Quartz

sand

25 35.5 25 2650 40 12.8 7.5

Mudsto

ne

13 23.3 10.8 2400 30 2.8 2.8

Sandy

mudsto

ne

7 24.2 12.5 2500 41 6.8 4.1

2 coal 2.8 14.8 6.06 1400 35 2.1 1.8

Fine-

sandsto

ne

4 37.4 26.9 2700 34 18.4 7.8

Sandy

Mudsto

ne

2 24.2 12.5 2500 44 6.8 4.2

Mid -

sandsto

ne

4 34 21.4 2450 36 18.4 6.5

Sandy

mudsto

ne

4 24.2 12.5 2550 44 6.8 4.1

3+4

coal

4 14.8 6.06 1400 38 2.1 1.8

Sandy

mudsto

ne

4 24.2 12.5 2600 46 6.9 4.1

5 coal 4 14.8 6.06 1400 40 2.1 1.8

Sandy 8 24.2 12.5 2650 48 6.9 4.2



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mudsto

ne

Limesto

ne

9 30.4 16.5 2450 46 14.6 7.2

2.2 Results and analysis

2.2.1 The vertical stress analysis of the coal rock along the roadway

Fig.8 10m excavation stress cloud

Fig.9 40m excavation stress cloud

Figure 8-9 respectively reflected the stress distribution rule when neighbor coal

mining advanced to 10m, 40m. Disturbed by coal mining, the original stress

equilibrium state inside the coal rock was broken, the stress will find a new

equilibrium state, and this process is called stress redistribution. During the mining

advancement, the additional stress generated by the rock under the impact of coal

mining resulting in that the coal rock showed obvious regional characteristics, shown

as figure 9, that are the stress increasing zone (compression of front of the working

face, as blue area in the clouds figure), stress reducing area (This area rock stress is

less than the initial stress, in unloading state, as red area in the clouds figure, the coal

rock occurred expansion deformation). However, due to the limitations of numerical

calculation, cloud no stress recovery area (cause by the caving of coal roof), these

areas constantly adjusted and repeated with the coal mining, the specific features are

as follows.

Rock mass stress increased area: The area is located near the border of the coal



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mining face, Stress level of coal rock was significantly increased. Under the

centralized stress, the rock exposed in the goaf was affected by the tension effects

parallel to the rock surface, and born a large horizontal compressive stress within a

certain distance of the the goaf, leading to the coal rock produced a large number of

joints and cracks, and with the increasing of centralized stress, the cracks may be

closed.

Rock mass stress reduced area: After coal mining, in order to resist the uneven

deformation caused by the unloading, the rock shifted the stress direction through

adjust itself, formed a dynamic arch structure. It passed outside mine pressure to the

surrounding rock, its supporting point located in the area of stress concentration. The

stress reduced area distributed in the inner side of the structure and located near the

goaf and all in the unloading state, there is a lot of tension cracks. The rock located in

the stress reduced area will not be affected by the pressure of the arch outside of the

mine, its own weight will not affect the strata outside of the arch.

Rock mass stress recovery area: In this area the rock additional stress will

gradually increase, there is a trend to recover to the initial stress. The reason is that

with the coal advance, the top roof will be cyclical broken, the rock continue caving,

so the coal floor seam suffered the re-compaction of gangue.

2.2.2 The coal rock mass displacement analysis

Fig.10 Displacement contour plot clouds as excavation 40m




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Fig.13 Displacement vector that the direction along the roadway as excavation 70m

The Fig.10-13 shown the longitudinal displacement distribution law of the coal

along the roadway respectively when the working face advanced to 40m, 70m and

100m. When the coal excavated to 40m, the mining disturbance is less impact on the

rock mass, the unloading range and the displacement range are small. But with the

working face forward, the overburden on top of the goaf due to the increasing range

of the unloading, the rock withstand loading and displacement were gradually

increased, displacement values can be up to 2.78m. During this period the uneven

subsidence and dislocation in the horizontal direction of the rock strata will produce

lot of vertical cracks and fissures delamination may increase coal seam permeability

significantly. In FLAC-3D calculation and analysis, the longitudinal displacement

reflected the delamination fractured development caused by the coal rock subsidence.

The bottom slab appeared the phenomenon of floor heave, increased the permeability

of bottom slab, and also increased the gas storage and transport channels.

It is evident that the moving trends at different locations strata in figure 16,

due to stress concentration caused a partial compression in the goaf corner, both ends

of the rock are under pressure to produce displacement away from the the goaf. The

rock below the goaf has a trend to whole movement upward, in the transition region

of compression and expansion zone there are unsynchronized displacement in each

strata, based on the original fissure will produce many secondary cracks, became a gas



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adsorption, migration favorable channel, but also offered the possibility for the

realization of gas extraction.

2.2.3 Volumetric strain increment analysis of the coal rock

Fig.14 Volumetric strain increment when mined 10m

Fig.15 Volumetric strain increment when mined 90m

Show as Fig.14-15, with the coal mining, rock at the top and bottom of the goaf

will produce swelling deformation, in the open-cut hole and the support pressure area

front of the coal wall will produce compressive deformation, it is consistent with the

vertical stress distribution that will produce compressive deformation in the stress

concentration area. The volumetric strain cloud of each stage excavation is

corresponding to its vertical stress cloud, and the volumetric strain increment is

nonlinear increasing in the advance process. After excavated to 90m along the

roadway, the volumetric strain increment is up to 3.26e-2, the maximum value is in

the red region of the coal roof, and subjected to the full impact of mining, resulting in

damage. In addition to the transition zone of the volumetric strain increment that from

the compression area to the expansion area, there are dramatic changes in the strain

gradient and will exist a large number of through-cracks.

2.2.4 Coal rock shear stress analysis



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Fig.16 the maximum shear stress cloud when mined to 60m

Fig.17 the maximum shear stress cloud when mined to 90m

Show as Fig.16-17, after the coal mining, the second distribution of the coal

rock stress will be caused inevitably. When mined to 60m, the front coal wall of the

working face will have a great stress concentration, its shape is consistent with the

simplified model in chapter 2. When mined to 90m, the arch range of maximum shear

stress increased significantly, the maximum shear stress that around the goaf appeared

significant concentration phenomenon in the front coal wall and the open-cut hole, it

reflected the force transmission mechanism of the coal rock arch structure.

Experiments show that most of rock destruction are shear failure, and comply with

Moore- Coulomb criterion. Therefore, in the vicinity of the arch will exist a large

number of shear fractures, and when the external force increased to a certain extent,

the native fissures and newborn fractures in rock were extended or cut through, will

eventually lead to the rock destruction.

The rock on the maximum shear stress arch is the main load-bearing structure of

the rock mass, in its inside is densely region of the fractures development, is also the

most serious damage area in the rock. With the working face advancement, the

pressure arch constantly adjusted its own stress state, once the external loads exceed

their carrying capacity, the coal rock will produce caving again, and the outside arch

will form a larger arch body to maintain the stability of upper coal rock.



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3 Conclusions (1)Based on the evolution of coal mining into the arch structure, proposed a

simplified model of rock mass structures, and gave the loading distribution form of

the structure combined with the actual situation, using of the substructure method, the

elastic center method and the superposition principle of the structural mechanics to

obtain the internal force analytical solution of the structure.

(2)Before the coal is mined, the rock mass is in three-dimensional stress

equilibrium state, the distribution of internal stress is uniform and gentle. With the

coal mining, the internal stress equilibrium state of the rock mass is broken, the

stresses is redistributed. In the process of working face advancement, the rock

additional stress generated by the mining resulted to the coal rock mass showed three

obvious regions: increased stress area, reduce stress area and recovery stress area.

These three areas adjusted constantly and repeat appeared with the working face

advancement. With the increase of extraction distance, the rock stress bubble was

transited from the Initial arch to a parabolic gradually, finally formed the saddle shape.

The variation rules of the mining rock mass displacement field is corresponding with

the stress field, the displacement of the roof slab is along with the increases of

extraction step, the displacement of the bottom slab will be some floor drum. The roof

slab caving will be re-compacted, but not be restored to its original state.

(3)The rock volume strain increment reflected the rock mass deformation in

different regions, when the changing amount reaches a certain value the coal rock will

produce fissures, resulting in damage, improve permeability. The maximum shear

stress cloud reflected the characteristics of coal rock arch structure, verified the

reasonableness of the coal rock structure system simplify model that proposed in this

paper, and the rock mass inside the arch stress is a enrichment fractures area.

Acknowledgement This paper is supported by National Natural Science Foundation of China (51274185).

Corresponding Author is ZhangMei (1973-), China,hebei province,baoding city,

associate professor. Mainly engaged in geotechnical engineering and mining

engineering

References [1] Jiang Yu-chuan, Xu Shuang-wu, Hu Yao-hua. Structural Mechanics[M]. Science Press. 2008

[2]Liu Tian-quan. Influence of mining activities on mine rockmass and control engineering.[J]

Journal of China Coal Society. 1995,20(1):1-5.

[3]Xie He-ping,Peng Su-ping, He Man-chao. Deep Mining basic theory and engineering

practice[M]. Science Press. 2006.



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Based on the Perspective of Construction

Contract of Project Quality Management

Research

YANG Xiao-liang1

1. Tianjin University Renai College, China

Abstract Aiming at the quality problems appear constantly in the field of construction

engineering in China, this paper analyzes the perspective of construction contract and

expounds the function of the construction contract in the engineering quality management.

Compare the 2013 edition of the "construction contract (model text)" with the 1999 version of

the FICIC "construction contract conditions" in the engineering quality of the relevant

provisions of the analysis, to find the two contract model in the project personnel structure,

engineering authority, sub-contractor selection, employer supply materials and mechanical,

warranty five aspects of the difference. These differences will be the research direction of

improves the quality of the construction contract clause.

Key words: Construction contact; Quality management; Engineering quality clause

1 Introduction:

Since 1980s, the quality problem in our country has been widely recognized by the

whole society, but at the same time the quality of the project is still very prominent.

According to Yu and Lu (2012), the construction process of the project is the process

of the contractor's performance of the construction contract. The contractor should

according to the contract, make the relevant resources turn into the construction

capacity. Then, function in construction materials, and ultimately to achieve the target

of the contract. Therefore, quality management is one of the main functions of the

construction contract. In view of the construction contract, the quality of the study of

Research Paper



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engineering quality improvement has a very important practical significance.

The main use of the field of engineering construction in China is the construction

contract (model text) issued in 2013. In this paper, the model text and the International

Federation of Consulting Engineers (FIDIC) in 1999 to prepare the "Conditions of

Contract for Construction " (hereinafter referred to as the "new Redbook") as the

research object, get research conclusion (Construction contract conditions, 2002).

Main body:

1.Engineering project quality management in the contract

In order to critical analysis the impact of construction contract for the quality of the

project, this paper of demonstration text and new Redbook in terms of quality are

summarized, tries to discuss the foundation of construction contract in the quality

management.

1.1 the construction contract is compulsory for the contractor to develop the

quality management system. Demonstration of the text paragraph 5.2.2 the Contractor's quality management and

new Redbook item 4.9 "quality assurance", explicitly require the Contractor shall

establish the quality assurance system, and the preparation of documents related to the

measures. Model text requires the contractor will submit relevant documents to

contract and supervision. What’s more, the new Redbook agreed engineers have the

right to review any aspect of quality assurance system. The establishment of the

quality assurance system can effectively improve the engineering quality, promote the

continuous improvement of the quality management system, and ensure the effective

operation of the organization, so as to better meet the needs of the owners, improve

the level of production management.

1.2 the construction contract shall clearly define the cooperation frame and

behavior of the relevant parties in the quality management. Construction project is a process of multi participation, in the process, the employer,



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the contractor, the supervisor and the sub-contractor to cooperate with each other, to

achieve quality objectives. Therefore, the establishment of mutual relations and

mutual restraint of the collaborative relationship, not only related to the organization's

efficiency, but also directly affect the quality of the project.

First of all, the construction contract clearly the quality of the parties involved in

the quality management of the work responsibilities and rights. For example, the

supervisor of the contractor supervision and inspection, the contractor sub-contracting

the behavior of management and organization are in the construction contract agreed.

These conventions constructed the basic framework of the unified management of the

construction site. Second, the construction contract specification for parties quality

management in the quality of the work process.

For example, the constructions contract for the employer to supply the material and

equipment of the approach process, including the time, inventory, inspection and

reception. In the process of completion and acceptance, the construction contract has

been standardized to the acceptance time, the acceptance process, the participants and

the receiving project. These form the behavior of the relevant parties involved in the

quality of the construction contract.

1.3 the main factors affecting the quality of the construction contract. Although each project has different characteristics, but in the process of project

construction, for the control of the quality of the five types of factors, the

requirements are the same, so the construction contract model will be the common

requirements of the contract terms. All engineering projects must comply with, so as

to regulate the construction market, improve the overall quality of the project.

On the human factor, the construction contract requires that the main management

personnel and technical personnel should have qualification. The other personnel

should have the ability to perform their duties. Build up the replacement process of

project manager and general supervision engineer. What’s more, establish the code of

conduct in order to better standard construction site personnel.

Construction materials and equipment are mainly two sources, the employer

provides and the contractor procurement, one of the sub-contracting procurement of



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the case into the contractor procurement. Construction contract for two cases of

material equipment approach, inspection, receiving the relevant process to make the

detailed provisions of the construction process of material testing, equipment testing

and on-site custody of the agreement, and the strict rules for the completion of the

procedures.

Construction contract to the construction method come up with relevant standards.

Requires the contractor to develop a reasonable, safe and reliable construction method,

to ensure the smooth implementation of construction and quality objectives of the

project.

The control of environmental factors in the construction contract is mainly reflected

in the requirements of the contractor to the construction site of the natural

environment full investigation. Establish a complete quality assurance system, and to

implement the unified management in the field of engineering. In order to provide the

necessary living conditions, safe working environment and reasonable treatment for

the project construction personnel.

1.4 the quality responsibility of the main parties involved in the construction

contract.Contractual obligations, and then create the responsibility. In the process of

construction, the construction contract is the important basis for the quality

responsibility. In the process of project construction, the main participants are the

employer, contractor and supervisor, and the three parties shall bear the

responsibilities of their respective duties according to the contract of construction, and

accept the quality inspection (Jin, 2012). In the event of quality problems, the main

responsibility of the subject will bear the responsibility, subject to the relevant party's

claim. Therefore, the fair contract in the construction of the parties to the quality of

responsibility, to improve the quality of the project and the project quality

management level is of great significance.



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2 Analysis of differences between model text and new Redbook in terms of

quality

Compared the model text and new red book, the difference can be derived from the

two contract agreed on in quality management. These differences reflect the

differences in the process of project management in China and the international

practice, this analysis can be found in the following characteristics:

2.1 the difference of personnel structure between model text and new red book. The main participants in the project construction of the model in the text is divided

into contract, contractor and supervisor third party, each party has its own employees.

However, the supervisor is often based on the contract award instructions to the

people to carry out the work. Not in accordance with the terms of the contract as

independent third party for project construction supervision. New red book

construction participants are including the employer's personnel and the contractor's

personnel, engineers belonging to the employer's personnel and the employer's

representative to exercise powers of project management. This personnel structure

more in line with the characteristics of the construction project.

2.2 Compared with the model text, the powers of engineers are enhanced in New

Redbook New Redbook agreed by the engineer's management behavior are regarded as

approved by the employer, to give engineers the right to change the content of the

engineering test, requirements engineers and assistant should have qualifications, also

did not make the replacement engineer agreed, which fully embodies the position of

the Engineer in project management, and the importance of the quality of the project.

Therefore, Zhang and He (2003) explained that the international engineering attaches

great importance to the choice of engineers, usually more consider the ability of

engineers, and less consideration of the cost of consulting.

2.3 the subcontractor selection, in terms of the new red book fairer. The model text of the agreement is vague, only in the special provisions of the

agreement. Due to the construction enterprises in the construction contract signed in a



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weak position, this way allows the employer to get more power in the choice of

sub-contractors. The new Redbook clearly that the employer nominated subcontract

concept, and the process of determining the sub contract specifies. In particular, the

contractor may reasonably object to the description of the nominated sub-contractor,

and avoid the risk of the employer to the contractor's failure to specify the risk caused

by the failure of the project to make the contract more reasonable and fair.

2.4 Contract (employer) provide the conventions of the materials, machinery,

demonstrative text is paying more attention to the results, the new Redbook pays

more attention to fairness. In the model text, the contractor shall strictly examine the employer's material and

machinery, and to ensure the quantity and quality of the materials in the entry when

the supervision is assisted. But, the new red book more likely by the employer to

provide materials and machinery to bear the relevant responsibility.

2.5 The agreement of the guarantee is a bit complicated. Huang and Chen (2014) stated that the model text introduces the concept of the

defects in the FIDIC series contract, in the form of the defects liability period.

However, in order to meet the requirements of the relevant laws, the model text

continues to retain the warranty period of the agreement, which makes both the time

and the work of the contents of a certain overlap (Lu, Cheng and Lu, 2012).

3. Conclusion

The project is to complete the construction in the construction contract

agreement. The quality of the construction contract is an important constraint in the

process of the formation of engineering quality. Reasonable quality terms can play a

vital role in promoting the engineering quality.

In this paper, the effect of quality clause on the quality management of the

project is summarized. According to the compare model text with new Redbook,

obtained in the project personnel structure, engineer permissions, contract selection,

contract people supply materials and machinery, warranty five aspects differences



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exist. These five aspects will be an important way to improve the quality of the model

text of the follow-up study.

Reference[1] Yu, Q. and Lu, Y. Research on supply chain coordination model of construction

enterprises based on value net. Construction economic, 2012(2): 88-91.

[2] Construction contract conditions. Beijing mechanical Industry Press, 2002

[3] Jin, G. Research on the quality of the construction contract in China. Jilin

University, 2012.

[4] Zhang, S. and He, B. FIDIC version of the conditions of contract for introduction

and analysis. China Construction Industry Press, 2003: 34-39.

[5] Huang, P. and Chen, N. Interpretation of the 2013 edition of the construction

contract six on the quality of the warranty period and the defect liability period.

Bidding and bid, 2014 (03): 13-15.

[6] Lu, J., Chen, H. and Lu, Y. (2012). Residential delivery after all relevant parties of

the responsibility for the quality analysis and countermeasures. Journal of

engineering management, 2012, 26(5):84-88.

ijgsw 2015 vol

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