Shear behaviour of GCL-sand interfaces under static and dynamic conditions

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PhD; 2023; Civil engineering

Geosynthetic clay liners (GCL) are unique geocomposites that combine the beneficial properties of bentonite clay and geosynthetics in providing effective hydraulic barriers in landfill systems. In landfills, GCLs form interfaces with soils and geosynthetics, resulting in inhomogeneity of the system. Inadequate shear strength mobilization at the interfaces results in translational failures in Geosynthetic Clay Liner (GCL). Interface shear strength of GCLs with the sand particles is predominantly influenced by the surface characteristics of the GCL, size and shape of the sand particles and their interaction mechanisms. These mechanisms change drastically with the hydration of GCLs and under repeated and dynamic loading conditions. This thesis examines the GCL-sand interactions and quantifies the interface shear strength under static and dynamic conditions with dry and hydrated conditions in sand. Illegal sandmining has resulted in the depletion of natural river sand and its scarcity for various constructional activities. To combat this issue, this study proposes the use of Manufactured sand (Msand) as a suitable subgrade or cover soil in landfills and evaluates its performance as an interfacing material with GCLs and compares it with the performance of river sand. Since the particle shapes of natural river sand and Msand are significantly different, a part of this thesis is focused on quantifying the shape parameters of the sands and investigating the effects of particle shape on the interaction mechanisms and shear strength of different GCL-sand interfaces.