Effect of static shear stress on the cyclic resistance of sands in simple shear loading

An experimental study of the effect of (initial) static shear stress on the undrained simple shear response of sands is presented. Liquefaction resistance of two sands, one generally contractive and the other dilative, over a wide range of density and effective stress levels was evaluated at various density and stress states. At a given density, the effect· of static shear on the cyclic resistance of sands is dependent on the type of stress–strain response that ensues during loading. The general notion that static shear increases the cyclic resistance of sands at relatively high densities is not valid if the sand is contractive at the denser state. The Kα correction factor for sand at 80% relative density may be as low as about 0.6 for strain-softening sand depending on the initial stress state. The routine industry practice of disregarding the Kα factor in dense sands may thus lead to unsafe designs in such materials. The Kα values measured under cyclic simple shear loading are compared to the Kα values ...