Shear Behaviour of Geosynthetic Clay Liner (GCL) Interfacing with Manufactured Sand

Abstract

In view of the problems of sand extraction and its harmful impact on coastal erosion, research now focusses on viable alternatives. Manufactured sand (Msand) has become an admissible alternative to be used in concrete instead of river sand. In countries like India, sand mining is illegal, considering the adverse effects it can cause to river basins. Replacement of river sand with Msand as a suitable subgrade or capping material in landfills needs to be investigated. When Geosynthetic Clay Liners (GCL) are used on sloping grounds, interface friction between GCL and the base soil becomes important to ensure bonding and arrest slippage issues. While the interface shear characteristics of natural sand with GCLs are well established in the literature, not many studies are reported on the interface characteristics of GCLs and Msand. This study is an approach towards understanding the interface shear strength parameters of GCLs with manufactured sand and compare them against those of river sand under identical loading conditions. To avoid the effects of morphology, identical gradation of both the sands is used in the tests. This gradation is arithmetic average of grain sizes of both the sands, which is achieved by tweaking with the proportions of different sized grains. Chemical analysis of both the sands is carried out for comparison using X-ray diffraction. A GCL with bentonite sandwiched between a woven geotextile on one side and nonwoven geotextile on the other side is used in the tests. Interfacing surface is a nonwoven geotextile in all the tests. Interface shear tests are carried out on river Sand-GCL and Msand-GCL interfaces to obtain adhesion and interface friction angle of both these interfaces. Further, damage assessment of GCL surface due to interaction with these two different types of sands is carried out using Optical Microscopy and image analysis. Results from these studies provided clear directions towards the replacement of river sand with Msand in landfills in terms of interface friction characteristics and the comparative surficial changes in GCLs with the indentation of sand particles, which can give confidence about sand replacement.