Effect of Reinforcement on Soil

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Effect of Reinforcement on Soil

1Neeraj Singh Parihar,

2Rajesh Prasad Shukla and

3Ashok Kumar Gupta

1 Assistant Professor, Department of Civil Engineering, JUIT, Waknaghat, (H.P.), 173234. India 2.Department of Earthquake Engineering, IIT Roorkee, India, [email protected] 3.HOD, Department of Civil Engineering, JUIT, Waknaghat, (H.P.), 173234. India

Abstract

Increase in population with a tremendous growth rate has led to scarcity of good land for construction and it has forced the engineers to improve the capacity of soil by means of reinforcement. Geotextiles have emerged as a good and economical alternative for soil reinforcement. This article presents the result of triaxial testing conducted on c- soil samples reinforced with geosynthetic. Woven and non-woven

geosynthetics were used in the form of sheet and thread. Effect of type of geosynthetic, confining pressure, number of layers and content of geotextile thread have been considered in analysis. The stress-strain behaviour of soil has improved with the addition of geotextiles. Increase in number of layers and confining pressure has led to the improvement in the performance of reinforced soil. Deviatoric stress has increased with increase in number of layers and confining pressure. Optimum amount of geotextiles threads are found to be varying from 5% to 10% by weight of soil. Result of study are presented in the graphical form. Keywords: Reinforcement, Geotextile, Woven, Nonwoven, Soil, Triaxial, Confining pressure

1.Introduction Nowadays there are various alternatives available to increase the strength and stiffness of the weak soil and to improve the behaviour of soil under various loading and environmental conditions. Geotextiles are most widely used sheet materials for reinforcement and there are wide verities of geotextiles available in the market. Geotextile reinforced soils are very frequently used in various civil and environmental engineering projects because geotextiles are cost effective and environmental friendly. Reinforcements and soil together are treated as composite material to study the behaviour of reinforced soil [1]. In case of unreinforced soil samples, failure occurs along a planar shear plane, whereas reinforced soil samples fail due to bulging between neighbouring geotextile layers [2].

There are various studies available on sand and clay reinforced soil in literature. Triaxial test are one of best laboratory test to determine the effect of reinforcement on the behavior of soil.

Various triaxial test on sand have been performed byHaeri et al. 2000 [3], Chandrasekaran et al. 1989 [4], Gray and Al-Refeai 1986 [5], Zhang et al. 2006, 2008 [6], Latha and Murthy 2007 [7], Tafreshi and Asakereh 2007 [8], Wu and Hong 2008 [9], Tuna &Altun 2012 [10], Nguyen et al. 2013 [11], Parihar

et al. 2015[12] to study the various aspects of reinforcement. Several studies have been also conducted on clay by various researchers (Ingold and Miller 1983 [13],Noorzad and Mirmoradi 2010 [14], Fabian and Foure 1986 [15], Al-Omari et al. 1989 [16], Fourier&Fabian 1987 [17]).Test results of earlier studies on reinforced soil have revealed that the behaviour of reinforced sand depends on the various parameters such as reinforcement arrangement, confining pressure, specimen size and reinforcement characteristics (spacing, strength, stiffness and form).

Many additional factors affect the behaviour of reinforced clay such as permeability of reinforcement, moisture content, drained/undrained loading conditions and relative compaction. Reinforcement contributes to the additional strength, flexibility and ductility in reinforced soil so failure of material changes from brittle to flexible or ductile. Post peak strength loss also reduces with the addition of geotextiles. There are various studies conducted in the past to determine the reinforcing behaviour of reinforced sand and clay and only a few studies are available on reinforced c- soils. In the present study, an attempt have been made to determine the effect of number of layer and confining pressure on the peak stress of a well graded compacted c- soil.

2.Material used in the Study

2.1 Soil

A c- Soil used in present study and it is collected from Domehar district of Himachal Pradesh, India. Index properties of soil are shown in tabular form in table1. Grain size distribution of soil are shown in figure 1.

Table.1: Index properties of soil

Properties Value

Liquid limit 41.80% Plastic limit 21.85%.

Plasticity Index 20.05% Effective size 0.019 mm

Cohesion 52.43 kPa Angle of internal friction 8.840

OMC 17.11% Max. dry density 1.7331 gm/cc

International Journal of Applied Engineering Research, ISSN 0973-4562 Vol. 10 No.55 (2015) Research India Publications; httpwww.ripublication.comijaer.htm

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Fig. 1: Grain size distribution curve of soil

2.2 Geotextiles

Woven and nonwoven geotextiles were used in sheet and thread form in study. The geotextiles are bought from Virendera Textiles, Noida, Uttar Pradesh and shown in figure 2. Properties of nonwoven and woven geotextiles are shown in table 2 and table 3 respectively. Used geotextiles are resistant to various chemicals and microorganism found in earth and short term resistant to UV radiations as well.

(a)

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Fig. 2: Geotextiles used in study; (a) Non-Woven Geotextiles (b) Woven Geotextiles

Table 2:Properties of Non-woven geotextiles Properties Values

Mass Per Unit Area 120 g/m Thickness 120 GSM Tensile Strength CD 4.0 KN/m Elongation 80 % Grab Tensile Strength CD 0.30 kN CBR Puncture Strength 640 N Apparent Opening size 90 Microns

Table 3: Properties of woven geotextiles

Property Value

Tensile Strength 42 KN/m Elongation at Break 28 % Trapezoid rear strength 520 N Puncture strength 620 N Water Permeability 9.5 Apparent opening 0.075 mm Weight of Fabric 240 GSM

2.3 Triaxial apparatus

All test specimens of triaxial test are having diameter of 38mm and 76 mm height. Apparatus used in study is shown in Fig 3.

Fig 3: Triaxial test apparatus

3. Experimental Program and procedure

All soil samples were collected from Domehar district of Himachal Pradesh. Index properties of collected soil are determined in laboratory as per Indian standards. Grain size distribution, moisture content, consistency limit, and

compaction parameters were determined as per IS: 2720 (Part IV) -1985 [18], IS: 2720 (Part II)-1973 [19], IS: 2720 (Part V) 1985 [20] and IS: 2720 (Part- VII)-1980 [21] respectively. The geotextile sheet was cut into a circular shape of size 37.00 mm diameter. Geotextile arrangement used in tests is shown in figure 4.

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The specimens for triaxial test were prepared in laboratory using a metallic split mould with a detachable collar. Mould is having 38 mm and 76 mm of diameter and height respectively. A detachable collar, orthogonal to the vertical axis of the mould is connected at the end of the mould. Reinforcements of circular shape sheet were placed in the mould at variable height. A trial and error method was used to obtain the position (height of reinforcement layer in the soil sample) of geotextiles layer in triaxial sample. In trial- error process, the geotextiles were placed at arbitrary height from the base of mould and these height values are noted down in an observation sheet. The soil sample was compacted in layers using a tamping rod. After compaction process completed, soil sample was detached from sampler or mould and final positions (height from base) were again noted down in sheet. This procedure is repeated until geotextile sheets get the desirable position in triaxial sample.

Prepared soil sample was then placed on the pedestal of the triaxial apparatus for further testing. The test was carried out till the maximum value of the stress has been reached and stress v alue start reducing with strain. Unconsolidated Undrained triaxial tests on soils samples were carried out as per IS: IS: 2720 (PART 11) 1993 [22].

Fig. 4: Geotextile arrangement used in tests

4. Result and Discussion

4.1 Effect of number of layers and thread content on the

peak stress of reinforced soil

Peak stress is increased with increase in number of layers and thread content in soil samples. Peak stress is increased linearly when number of layers increased from zero to one and zero to two. Increase in peak stress is more when number of layers increases from two to three. Effect of number of layer on peak stress for woven and nonwoven geotextiles are shown in figure 5 (a) and (b) respectively.

Peak stress also increases with increase in threads of geotextiles. Optimum amount of threads are found to be approximately 10%. Effect of threads on peak stress is shown in figure 6.

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Fig. 5: Effect of number of layers on peak stress (a) woven geotextiles (b) nonwoven geotextiles

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Fig. 6:Effect of geotextiles thread % on peak stress of reinforced soil

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4.2 Effect of confining pressure on the peak stress of

reinforced soil

Peak stress is increased linearly with increase in confining pressure irrespective of number of layer and percentage of geotextiles. Effect of confining pressure is more for higher number of reinforcement. Effect of confining pressure on behavior of reinforced soil is shown in figure 7.

(a)

(b) Fig. 7: Effect of confining pressure on peak stress of soil (a)

woven geotextiles (b) nonwoven geotextiles

Peak stress increase linearly with increase in confining presuure pressure. Peak stress for 10 % and 15% geotextiles thread is approximately same for a particular value of confining pressure.Effect of confining pressure on peak stress of reinforced soil is shown in figure 8. It shows that optimum amount of geotextiles is approximately 10% of soil.

Fig. 8: Effect of geotextiles threads on confining pressure

McGown et al. (1981) [23] stated that the peak stress is increased with increase in confining pressure because increase in confining pressure leads to increase in frictional stress between soil and geotextiles. But, it can also be observed that on increasing the confining pressure beyond a certain limit, the difference in the peak stress values of different number of layers becomes less evident. This observation is well matched with Noorzad &Mirmoradi(2010) [24].

5. Conclusion

Index properties and all other laboratory tests were conducted as per Indian standard code. Both, woven and non-woven geotextiles were used as reinforcement and it was found that woven geotextiles are more effective compared to non-woven geotextiles to improve the peak shear strength of soil. With increase in number of layers and confining pressure, there is increase in the peak stress but becomes less evident at very high values of confining pressure. Peak stress increases linearly with increase in confining pressure irrespective of number of layers and percentage of geotextiles.Peak stress of reinforced soil increases linearly with increase in number of layers up to two l ayers but increasing number of layers more than two causes much higher increase in strength of soil. The optimum amount of the thread geotextiles is found to be approximately 10%. Increasing the confining pressure beyond a certain limit, the difference in the peak stress values of different number of layers becomes less evident. References

[1] Haeri, S.M., Noorzad, R., Oskoorouchi A.M., Effect of geotextile reinforcement on the mechanical behavior of sand. Geotextiles and Geomembranes 18, 385-402, 2000.

[2] Chandrasekaran, B., Broms, B. B. & Wong, K. S., Strength of fabric reinforced sand under axisymmetric loading. Geotextiles and Geomembranes, 8, No. 4, 293310,1989.

[3] Gray, D.H., Al-Refeai, T. Behavior of fabric vs. "ber-reinforced sand. Journal of Geotechnical Engineering ASCE 112 (8), 804-820, 1986.

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[4] Zhang, M.X., Javadi, A.A., Min, X. Triaxial tests of sand reinforced with 3D inclusions. Geotextiles and Geomembranes 24 (4), 201209, 2006.

[5] Latha, G. M. & Murthy, V. S. Effects of reinforcement form on the behavior of geosynthetic reinforced sand. Geotextiles and Geomembranes, 25, No. 1, 2332, 2007.

[6] Tafreshi S.N.M., and Asakereh A. Strength evaluation of wet reinforced silty sand by triaxial test International Journal of Civil Engineerng. Vol. 5, No. 4, 2007.

[7] Wu, C. S. and Hong, Y. S. The Behavior of a Laminated Reinforced Granular Column, eotextiles and Geomembranes, 26: 302-316, 2008.

[8] Ingold, T. S. & Miller, K. S. Drained axisymmetric loading of reinforced clay. Journal of Geotechnical Engineering, ASCE, 109, No. 7, 883898, 1983.

[9] Nguyen, M.D., Yang, K. H., Lee, S. H., Wu, C. S. andTsai, M. H. . Behavior of nonwoven-geotextile-reinforced sand and mobilization of reinforcement strain under triaxial compression. Geosynthetics International, 20, No. 3, 207225, 2013.

[10] Noorzad, R. &Mirmoradi, S. H. Laboratory evaluation of the behavior of a geotextile reinforced clay. Geotextiles and Geomembranes, 28, No. 4, 386392, 2010.

[11] Parihar, N.S., & Shukla, R.P. Unconfined compressive strength of geotextile sheets reinforced soil. International Journal of Earth Sciences and Engineering, Vol.8, No. 3, 1379-1385.

[12] Hou, J., Zhang, M. X., Zhou, H., Javadi, A. A. & Peng, M. Y. Experiment and analysis of strength behavior of soil reinforced with horizontal-vertical inclusions. Geosynthetics International, 18, No. 4, 150158, 2011.

[13] MoghaddasTafreshi S.N. and Asakereh A. Strength evaluation of wet reinforced silty sand by triaxial test. International Journal of Civil Engineerng. Vol. 5, No. 4, 274-283, 2007.

[14] Athanasopoulos, G.A. Effect of particle size on the mechanical behavior of sand-geotextile composites. Geotextile and Geomembranes 12, 225-273, 1993

[15] Shah S.J. &Shikha K.S. Determination of interface friction characteristics of different soil-geosynthetic combinations. Proceedings of Indian Geotechnical Conference December 22-24,2013, Roorkee, India, 2013.

[16] M. Kamalzare& R. ZIAIE-Moayed. Influence of geosynthetic reinforcement on the shear strength characteristics of two-layer sub-grade. ActaGeotechnicaSlovenica, pp39-49, 2011.

[17] S.C. Tuna, S. Altun , Mechanical behaviour of sand-geotextile interface. ScientiaIranica 19(4) pp 10441051, 2012.

[18] E.M. Palmeria Soilgeosynthetic interaction: modelling and analysis Geotextiles and Geomembranes, 27 (5), pp. 368390, 2009.

[19] D. Russell, V. Jones, N. Dixon Shear strength properties of geomembrane/geotextile interface

Geotextile and Geomembranes, 16 (1), pp. 4571, 1998.

[20] S.A. Tan, S.H. Chew, W.K. Wong Sand-geotextile interface shear strength by torsional ring shear tests Geotextiles and Geomembranes, 16 (3), pp. 161174, 1998.

[21] G.A. Athanasopoulos Effect of particle size on the mechanical behaviour of sand-geotextile composites Geotextiles and Geomembranes, 12 (3) (1993), pp. 255273

[22] Fourie, A.B., Fabian, K.J. Laboratory determination of clay geotextile interaction. Geotextiles and Geomembranes 6 (4), 275294,1987.

[23] Fabian K. &Fourie A. Performance of Geotextile-Reinforced Clay Samples in Undrained Triaxial Tests. Geotextiles and Geomembranes 4, 5363, 1986.

[24] McGown, A., Andrawcs, K.Z., Wilson Fahmy, R.F. and Brady. K.C. A new method of determining the load extension properties of geotechnical fabric. TRRL, report no. 104, Crowthome, England. 1981.


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