A DIRECT SIMPLE SHEAR DEVICE FOR MEASURING SMALL-STRAIN BEHAVIOR

A simple shear device named the double specimen direct simple shear (DSDSS) device was designed to investigate static and cyclic properties of soils at small strains, such as cyclic stress-strain loops, maximum shear modulus, G(max), secant shear modulus, G,, and the equivalent viscous damping ratio, lambda. Cyclic shear strains between 5 x 10(-4) and 2 x 10(-2)% were successfully applied and measured. Such measurements of very small strains were achieved by completely eliminating the friction of the load-transfer mechanism and by reducing the effects of the mechanical compliance of the device to practically zero. This was facilitated by using a special configuration of two parallel specimens. The performance of the DSDSS device was examined first by testing rubber dummy specimens of different stiffnesses and then by conducting a series of tests on kaolinite clay consolidated under different vertical consolidation stresses and overconsolidation ratios. The results produced by the new device show very consistent trends and are in good agreement with equivalent data obtained by others using other types of tests and equipment.