Specimen Size Effect in Simple Shear Test

This paper presents the results of a laboratory investigation of the influences of height to diameter ratio and membrane stiffness on the behavior of clay in the NGI simple shear apparatus. The study included 21 strain-controlled, constant volume, monotonic loading, (static) tests on undisturbed specimens of medium-stiff clay. The clay was sampled in a special 200-mm ID research piston sampler. The testing program included use of three different height to diameter ratios and two types of reinforced rubber membranes for clay specimens at overconsolidation ratios of one and 10. The nominal height of the specimens was kept constant at 16 mm with diameters of 50 mm, 80 mm and 115 mm. The experimental results show that neither the height to diameter ratio nor the membrane reinforcement types used have any significant influence on the static-stress behavior measured in the NGI simple shear test.