Effect of initial stress state on the cyclic simple shear behaviour of sands

Liquefaction resistance of a sand under cyclic simple shear loading is assessed, and its dependency on the levels of confining pressure and static shear stress are investigated. The sand tested is strain softening over a range of initial states and therefore is highly susceptible to liquefaction under cyclic loading. It is shown that the K, factor is dependent not only on the confining stress level, but also on the level of initial static shear and density. K, factors reported in the literature may lead to unsafe designs if initial static shear stresses are present in the sand. The general notion that static shear increases the cyclic resistance of dense sands is not valid, if the sand is contractive at the dense state. Presence of static shear stresses seriously infringe on the cyclic resistance of the tested Silica sand over a wide range of density states. Even though the current empirical static shear correction factors underestimate the cyclic resistance of dilative sands by a wide margin, they may overestimate the liquefaction resistance of contractive strain softening sands.