SHEAR STRENGTH TESTS OF COMPACTED GRAVEL SOILS FOR GCls PROTECTIVE LAYER

Hydrated geosynthetic clay liners(GCls) are the excellence anti-seepage material. But they exhibit extremely low shear strength at the same time. To improved the disadvantage, a protector that adequately backfill over the GCL is set so as to consist of composite liners system. The artificially graded gravel soils are taken from natural sediment. The compacted gravel soils instead of clay are as a protective layer of GCls liner. The compacted gravel soils are selected according to the requirement of the code. They are put into the direct shear apparatus under the GCL with a hydration degree of, respectively, 50% and complete saturation. The direct shear friction tensile tester(TGH) is used in this paper. The experiments are performed. The results show that the shear strength of compacted gravel soils is far more than the contact surfaces that are consisted of compacted gravel soils with hydrated GCL.The shear strength of the contact surfaces is decreasing with the increasing of GCls' moisture content. So it is effective to release the pressure of GCls with the help from high bearing capacity of wide grading gravel soils according to the principle of stress diffusion in soil.