Effect of shear displacement rate on internal shear strength of a reinforced geosynthetic clay liner

Torsional ring shear tests were performed to evaluate the effect of shear displacement rate on the internal shear strength of a needle-punched geosynthetic clay liner (GCL) under different normal stresses. The test results suggest that the internal shear strength of the needle-punched GCL depends on the following three factors: (i) resistance against reinforcement fibers pulling out and/or tearing; (ii) amount of positive pore-water pressure induced during shear; and (iii) bentonite water content at the time of shearing. The laboratory tests indicate that the net effect of these three factors result in the peak internal shear strength being less sensitive to sheer displacement rate at normal stresses between 200 and 400 kPa than at normal stresses less than 200 kPa. Shear displacement rate appears to have little influence on the residual internal shear strength regardless of normal stress. The amount of shear displacement required to reach the peak and residual internal shear strengths is dependent on the shearing normal stress, shear displacement rate, and quantity of needle-punched fibers.