analysis of strength characteristics of soil

ANALYSIS OF CLAYEY SOIL REINFORCED WITH

RECRON 3S (Polyester) Fiber

ByB101184 – M Akshay KumarB101501 – B SandhyaB101580 – P UmamaheswariB101570 – D Manoj KumarB101590 – B Akhil Naik

09-05-2016 1

Under the Guidance of

Mr. Ranadheer Sagi(Head of the Department)

Contents

1 Theme

2 History of development

3 Methodology

4 Tests conducted

5 Results

6 Conclusion

7 References

09-05-2016 2Dept. of Civil Engineering, RGUKT - Basar

ThemeThe objective of this project is to investigate the use of fibres as

reinforcement to soil and evaluate their effect on Dry Density and ShearStrength of soil.

This includes: i. Analytical study on Fibers and Methods of Inclusion

ii. Getting the engg properties of proposed soil and fibreiii. Lab tests to find optimum fibre content

This aims at identifying optimum fiber content in terms of Length offiber and % fiber by weight of soil.


Need for project

Soil properties vary a great deal and construction of structures depends a lot on thebearing capacity of the soil.

Hence, there is a need to improve the strength of the soil by making it uniformlygraded which makes it easier to predict and even improve the strength of the soil.

But, mixing different types of soils together to improve the soil strength propertiesand replacing the inferior soil entirely is very expensive.

Therefore we have to look upon the alternatives.


History of development

Romans developed soil reinforcement based on the principle of plant roots that impartstrength to the beneath soil.

This technique was also used in the construction of THE GREAT WALL OF CHINA.

In 1966, A geotechnical researcher, Er. Vidal innovated the soil reinforcementmethods and developed the principles.

He nearly built 4K structures in around 37 countries across the world.

In recent times, this technique was attracted by the use of synthetic fibres.

Though very old, still does not has a scientific standard and relatively a new technique.


SELECTION CRITERIA:

After we reviewed many fiber reinforcement papers, we determined that the fiber selection parameters were the following:

• It must not be a hazard to its surroundings.

• It should not degrade so easily in the soil.

• It must be easily obtainable and inexpensive.

• Its preparation and inclusion method should be simple.

• It must work with the selected soil.


METHODOLOGY – For selection of Fiber

Fibres

Natural

Man-made

Coconut coir fibre

Sisal fibre

Bamboo Cane

palm

Jute

Polypropylene Fiber

Polyvinyl alcohol

Nylon Glass

Polyester

Polyethylene


What to select??

About proposed fibre – Recron 3S (Polyester)

100% synthetic – No natural constituent It’s a polymer – Monomer being Propylene Thermoplastic – Plasticity Temperature Transformed from 85% propylene By product of petroleum refining Prone to sunlight and fire. Resistant against abrasion, chemical and biological reactions. Mostly used as a secondary reinforcement to concrete.


09-05-2016 Dept. of Civil Engineering, RGUKT - Basar 9

Available Length Product Type Bag Size Price per Kg

6mm CT 2012 125 gr 450 Rs

12mm CT 2024 125 gr 450 Rs

18mm CT2436B, CT2436 450 gr 250 Rs

12mm CT2424B, CT2424 900 gr 400 Rs

Different lengths available in Recron 3S:

Source: Extracted from the broacher of Recron 3S fiber. Manufacturer: Reliance industries ltd

As 18mm fiber is not suitable for laboratory experiments, we have chosen to use rest of the types i.e. 6mm and 12mm fiber.

We have purchased the Recron 3S (Polyester) fiber manufactured by Reliance Industries Limited from Vasanth enterprises private limited, Punjagutta, Hyderabad.

Recron 3S – 6mm fiber Recron 3S – 12mm fiber


S.No. Property Value

1 TypeCT2012 and

CT2024

2 Length 6mm and 12mm

3 Cross Section Triangular

4 Colour White

5 Effective Diameter 35 – 40 microns

6 Melting Point 162 – 167° C

7 Flash Point >329° C

8 Relative Density 0.89 – 0.94 g/cm3

9 Tensile Strength 350 MPa

General specifications:

Recron 3S –Polyester fiber09-05-2016 11Dept. of Civil Engineering, RGUKT - Basar

Method of orientation


1. Oriented fiber reinforcement:In this type of orientation the fibers are arranged in some order and all the

fibers are placed in the same orientation. The fibers are laid layer by layer. Continuousfibers in the form of sheets, strips or bars etc. are used systematically in this type ofarrangement.

2. Random fiber reinforcement:This arrangement has discrete fibers distributed randomly in the soil mass.

The mixing is done until the soil and the reinforcement form a more or lesshomogeneous mixture. Materials used in this type of reinforcements are generallyderived from paper, nylon, metals or other materials having varied physical properties.

Oriented vs RandomOriented Random

1. Fibre inclusion requires high work and energy i.e. Not easy to add and mix

2. Similar to steel reinforcement in concrete.

3. Strength distribution is uniform over soil layers but not over soil mass.

4. Lesser ductility.

5. High Chances of formation of potential failure planes.

1. Fibre inclusion requires comparatively less work and energy i.e. Easy mixing

2. Similar to fly-ash reinforcement in concrete.

3. Strength distribution is more or less uniform over entire soil mass.

4. Higher ductility.

5. Less chances of formation of potential failure planes.


Mechanism

1. Soil matrix and Fibre surface interaction

2. Soil particles and Fibre surface interaction



METHODOLOGY – For analysis

Parent soil is tested for its index properties, dry density by proctor compaction test and shear strength were carried out as per the procedures and guidelines laid down in Indian Standards Codes of practice.

A total of sixteen samples (8 with each length of fiber) of soil – Recron 3S fiber mixture were made (0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% of the total dry weight of the soil).

After the determination of various index properties of soil, Proctor compaction tests were conducted, followed by direct shear tests on the reinforced soil.

1. Atterberg limit :1.1 Liquid Limit Test:

Sample No 1 2 3

Weight of empty Can in gms 10 9 10

Weight of Can + Wet soil in gms 28 26 35

Weight of Can + Dry soil in gms 25 22 29

Weight of soil solids 15 13 19

Weight of pore water 3 4 6

Water Content (%) 20 30.76 31.57

No of blows 57 28 15


15

17

19

21

23

25

27

29

31

33

0 5 10 15 20 25 30 35 40 45 50 55 60

Mo

istu

re C

on

ten

t (%

)

No of Blows

# of Blows vs Moisture Content

From Graph:Liquid Limit = Moisture content corresponding to 25 blows = 28.6%

LL = 28.6% < 35% therefore, the soil is Low Compressible.


1.2 Plastic Limit Test:

Sample No 1 2

Weight of empty Can in gms 9 10

Weight of Can + Wet soil in gms 31 30

Weight of Can + Dry soil in gms 28 27

Weight of soil solids 3 3

Weight of pore water 19 17

Water Content (%) 15.78 17.64

Results of Plastic Limit Test on parent soil

Average Plastic Limit = 16.71 %Plasticity Index (PI) = wl – wp where, wl = Liquid Limit; wp = Plastic Limit

= 28.6 – 16.71= 11.89 %

Hence, the soil is Medium plastic. Since, Ip lies between 7 and 17 %.09-05-2016 19Dept. of Civil Engineering, RGUKT - Basar

1.3 Specific Gravity Test:

Sample Number 1 2

Weight of empty bottle (W1) in gms 65 65

Weight of bottle + Dry Soil (W2) in gms 75 76

Weight of bottle + Dry Soil + Water (W3) in gms 174 177

Weight of bottle + Water (W4) in gms 169 169

Specific Gravity (G) 2.0 2.2

Results of Specific Gravity Test

Average specific Gravity of Parent Soil = 2.1


1.4 Differential Free Swell Test:

Volume of Water (ml) Volume of Kerosene (ml)

Before Swell 100 100

After Swell 101 100

By this test, Swell is observed to be 1%.


2 Tests on Reinforced Soil

Fiber Content (%) 0% 0.1% 0.2% 0.3% 0.4% 0.5% 0.6% 0.7% 0.8%

Internal Diameter of Mould, d (Cm) 10.16 10.16 10.16 10.16 10.16 10.16 10.16 10.16 10.16

Mould height, h (Cm) 11.64 11.64 11.64 11.64 11.64 11.64 11.64 11.64 11.64

Mould Volume, V (Cm3) 944 944 944 944 944 944 944 944 944

Wt. of mould + base plate, Wl (gr) 4305 4305 4305 4305 4305 4305 4305 4305 4305

Wl + Compacted soil, W1 (gr) 5860 6060 6090 6120 6130 6140 6150 6140 6130

Wt. of Compacted soil, W1-Wl (gr) 1560 1760 1793 1810 1820 1835 1851 1840 1820

Bulk Density, γbulk = (W1-Wl)/V gr/cc 1.81 2.03 2.07 2.10 2.11 2.12 2.14 2.13 2.11

Water Content, W% 6.5 8.5 9.3 9.5 9.7 9.85 10.50 10.7 10.8

Dry Density, γd=Vt/[1+(W/100)] gr/cc 1.70 1.88 1.90 1.92 1.93 1.935 1.94 1.925 1.91

1. Proctor Compaction Test with 6mm fiber

Results of soil reinforced with 6mm fiber 09-05-2016 22Dept. of Civil Engineering, RGUKT - Basar

1.65

1.7

1.75

1.8

1.85

1.9

1.95

2

0 0.2 0.4 0.6 0.8 1

MD

D (

g/C

C)

Fiber Content (%)

Fiber Content vs MDD - 6mm Recron 3S

MDD vs Fiber…

0

2

4

6

8

10

12

0 0.2 0.4 0.6 0.8 1

OM

C (

%)

Fiber Content (%)

Fiber Contet vs OMC - 6mm Recron 3S

OMC vs FiberContent

Results of Compaction test with 6mm fiber


1. Proctor Compaction Test with 12mm fiber

Results of soil reinforced with 6mm fiber

Fiber Content (%) 0% 0.1% 0.2% 0.3% 0.4% 0.5% 0.6% 0.7% 0.8%

Internal Diameter of Mould, d (Cm) 10.16 10.16 10.16 10.16 10.16 10.16 10.16 10.16 10.16

Mould height, h (Cm) 11.64 11.64 11.64 11.64 11.64 11.64 11.64 11.64 11.64

Mould Volume, V (Cm3) 944 944 944 944 944 944 944 944 944

Wt. of mould + base plate, Wl (gr) 4305 4305 4305 4305 4305 4305 4305 4305 4305

Wl + Compacted soil, W1 (gr) 5860 5900 5950 6014 6070 6110 6090 6060 6055

Wt. of Compacted soil, W1-Wl (gr) 1560 1590 1650 1700 1760 1811 1790 1750 1750

Bulk Density, γbulk = (W1-Wl)/V gr/cc 1.81 1.84 1.91 1.98 2.04 2.09 2.07 2.03 2.02

Water Content, W% 6.50 6.90 7.60 8.20 10.10 11.60 12.2 13.0 13.4

Dry Density, γd=Vt/[1+(W/100)] gr/cc 1.70 1.73 1.78 1.83 1.86 1.88 1.85 1.80 1.79


1.68

1.7

1.72

1.74

1.76

1.78

1.8

1.82

1.84

1.86

1.88

1.9

0 0.2 0.4 0.6 0.8 1

MD

D (

g/cc

)

Fiber Content (%)

Fiber Content vs MDD - 12mm Recron 3S

MDD vs Fiber…

0

2

4

6

8

10

12

14

16

0 0.2 0.4 0.6 0.8 1

OM

C (

%)

Fiber Content (%)

Fiber Content vs OMC - 12mm Recron 3S

OMC vs Fiber…

Results of Compaction test with 12mm fiber09-05-2016 25Dept. of Civil Engineering, RGUKT - Basar

1. Direct Shear Test

Results of Direct shear test

Normal Stress(Kg/Cm2) Shear Stress (Kg/Cm2)

0% fiber 0.2% fiber 0.4% fiber 0.6% fiber 0.8%fiber

6mm Fiber 0.5 0.0244 0.0267 0.0309 0.0271 0.0262

1 0.0256 0.0279 0.0315 0.0311 0.0282

1.5 0.0323 0.0345 0.0363 0.0351 0.0343

12mm Fiber 0.5 0.0244 0.0263 0.0293 0.0278 0.0258

1 0.0256 0.0288 0.0320 0.0286 0.0278

1.5 0.0323 0.0351 0.0349 0.0339 0.0336


32

32.5

33

33.5

34

34.5

35

35.5

36

36.5

0 0.2 0.4 0.6 0.8 1

She

ar S

tre

ss (

10

-3 K

g/C

m2

)

% Fiber

Fiber Content vs Shear Stress

6mm Fiber

12mm Fiber

Results of Direct shear test with 6 & 12mm fiber09-05-2016 27Dept. of Civil Engineering, RGUKT - Basar

Fiber Content 0% 0.2% 0.4% 0.6% 0.8%

Cohesion, C

(10-3 Kg/Cm2)

6mm fiber 20.8 23.0 28.3 23.0 22.0

12mm fiber 20.8 22.3 26.1 24.9 22.5

18

20

22

24

26

28

30

0 0.2 0.4 0.6 0.8 1

Co

he

sio

n (

Kg/

Cm

2)

% Fiber

Fiber Content vs Cohesion

6mm fiber

12mm fiber

Results of Direct shear test with 6 & 12mm fiber09-05-2016 28Dept. of Civil Engineering, RGUKT - Basar

CONCLUSION :• The maximum dry density of soil when reinnforced with 6mm fiber is observed

at 0.6 % of fiber, where in case of 12mm fiber it is observed at 0.5 % of fiber byweight of soil.

• For 6mm fiber, the maximum dry density is increased from 1.70 to 1.94 gr/cc.,therefore the % increase in dry density is 14.11.

• When 12mm fiber is used the maximum dry density is increased from 1.70 to1.88 gr/cc., therefore the % increase in dry density is 10.11.

• Hence, 6mm (Optimum % = 0.6) fiber is effective.


(CONCLUSION Cntd…)

• The increase in the Shear strength (τ) is found to be 12.3% (From 0.0323 to 0.0363 Kg/Cm2 ) for 6mm fiber and 9.59% (From 0.0323 to 0.0354 Kg/Cm2) for 12mm fiber observed at OFC of 0.4%.

• The net increase in cohesion was found to be 36% (From0.0208 to.283) for 6mm fiber and 30% (From.0208 to0.0260 Kg/Cm2) for 12mm fiber observed at OFC of 0.4%.

• From this it can be concluded that 6mm fiber aparts more strength to the soil and is recommended over 12mm fiber.


References

1. Construction and building materialsJournal No : 30 (2012) 100–116 Website : www.elsevier.com/locate/conbuildmat

2. International Journal of science Technology & ManagementVol. No : 04, Spl Issue on. 01, Feb 2015 Website : www.ijstm.com

3. Journal of Rock Mechanics and Geotechnical EngineeringVol. No : 6, Issue on 2,Apr,2014 Website : www.sciencedirect.com

09-05-2016 31Dept. of Civil Engineering, RGUKT -

Basar

http://www.elsevier.com/locate/conbuildmat

http://www.ijstm.com/

http://www.sciencedirect.com/

Thank you..


analysis of strength characteristics of soil

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