International Journal of Civil and Structural Engineering Research ISSN 2348-7607 (Online) Vol. 7, Issue 1, pp: (119-128), Month: April 2019 - September 2019, Available at: www.researchpublish.com
An Experimental Study on CBR of Expansive Soil Subgrades using Geotextiles Pupalwad Arti Sudam1, M Padmavathi2 , K.Ravikumar3, M.Nagaraju4 1
Assistant Professor, Dept. of Civil Engineering, VNR Vignana Jyothi Institute of Engineering and Technology, Hyderabad, India (Corresponding Author, E-mail: artisp2012@gmail.com) 2
Assistant Professor, Dept.of Civil Engineering, JNTU Hyderabad, India (Email: mpadmace@jntuh.ac.in)
3
Associate Professor, Dept. of Civil Engineering, VNR Vignana Jyothi Institute of Engineering and Technology, Hyderabad, India (E-mail: kanapuram.ravikumar@gmail.com) 4
Material Engineer, Egis India Ltd, Hyderabad, India (E mail: mnr2878@gmail.com)
Abstract: The behaviour of the road surface depends upon the strength of the fill material and subgrade below it. Road construction on soft subgrade soil is a major issue affecting cost and scheduling of highway road projects. The strength of subgrade is most often expressed in terms of California Bearing Ratio (CBR) which is the ratio of test load to standard load at specified penetration by a standard plunger. In India the design of flexible pavement is primarily on basis of subgrade CBR (IRC 37-2001).Many techniques have been evolved to strengthen the highway soil subgrade. Among them stabilization techniques are most common. In the Present study stabilisation of soft subgrade soil is achieved by using geotextiles. The objective of this study is to find out an increase in strength mobilization in terms of CBR values, by conducting CBR tests on the subgrade soil when reinforced with geotextiles placed at different positions. Silty expansive clay soil and three varieties of geotextile (HP-370, PEC, and TS-50) are used in the study. CBR tests are conducted with the geotextile placed at different depths from top surface of soil in the CBR mould. Keywords: Geotextiles, CBR, Expansive soils, Subgrade and Woven & Non-woven geotextiles.
1. INTRODUCTION For every Civil Engineering construction like buildings, roads, bridges, dams etc, foundation should be very strong. To keep the foundation strong, the construction process on the soil which plays a vital role. If the shear strength of the soil is high then the foundation will be strong. But if the weak soil is encountered in the construction area then it requires strengthening the soil to withstand the loads from super structure along with the self-weight of soil. In general, if the site of construction encounters expansive soils, which are problematic soils always, then there will be a great need for stabilization of the soils. As a general practice, known to everyone, stabilization of such expansive soils is done by the use of admixtures, stabilizers and geosynthetic materials such as geogrids, geotextiles etc. Now-a-days in the construction of roads, the usages of geosynthetic materials are being introduced. A lot of research is ongoing on various types of natural and artificial geosynthetic/geomaterials for introducing at suitable depth of soils with multiple combinations to enhance the strength of the expansive soils. Synthetic non-woven geotextiles were used by Sivapragasam.C and Vanitha.S. (2010) for road pavements in Virudhunagar district of Tamil Nadu, placed at different depths of soil in single layer and double layers from top of the specimen. According to the study, synthetic non-woven geotextiles were placed at different depth of soil such as 3cm, 6cm, 9cm in single layer from top. Similarly in double layers at 3cm & 6cm, 6cm & 9cm, 3cm & 9cm. The improvement in soil bearing capacity is checked by CBR & UCC test. The results has shown that, single layer of geotextile introduced at center (mid depth) showed better performance than those samples with geotextile at other depths. Naeini, S.A. and Mirzakhanlari, M. (2008) have found that by placing the Non-Woven geotextile sheet (Fibertex F-32) at the middle of the sample height with granular soil has given higher CBR compared to placing the geotextile at top or bottom.
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