Effects of Stress History on Cyclic Behavior of Sand

ABSTRACT To investigate the possible effects of preshearing on the cyclic behavior of saturated sand, two series of cyclic static triaxial tests were performed. In the first series of tests, saturated samples were first subjected to small cyclic stresses having equal amplitudes on both sides of triaxial compression and extension until the pore water pressures increased to values less than the initial effective confining stress. The excess pore water pressures were then allowed to dissipate under the initial confining stress. This part of the stress changes represents the application of stress history to the sample. The samples were further subjected to cyclic stresses in order to observe the pore water pressure and shear strain behaviors as influenced by the previous stress cycle. It was found that the samples subjected to small preshearing developed less pore water pressures and shear strains on both sides of triaxial compression and extension. The second series of the tests were identical to the first series except for the application of a large shear stress to the sample on either sides of triaxial compression or extension during the preshearing. It was discovered that the sample subjected to large preshear on one side of triaxial loading, compression or extension, became stiffer on that side, but softer on the opposite side.