Seismic response of submarine slopes

The geological profile of submarine slopes on the continental shelf typically consists of normally to lightly overconsolidated clays with depths ranging from a few meters to hundreds of meters. The seismic stability of these slopes is often investigated with pseudo-static methods by reducing the dynamic loading to an inertial force applied as a static load. The simplifications introduced in these analyses hardly provide a satisfactory answer to the questions of instantaneous and permanent displacement, accelerations, excess pore pressures and especially triggering mechanism. In order to provide a realistic assessment of the behavior of the slope to seismic loading, it is necessary to describe the stress-strain-strength response under irregular cyclic loading. The SIMPLE DSS model is an effective stress model that is able to account for strength anisotropy, accumulation of plastic strains and generation of excess pore pressures during successive loading cycles. This paper will investigate the effects of different soil profile characteristics on the response of submerged slopes and determine which parameters are most important when evaluating their seismic stability. The effect of layering, and in particular thin very soft layers, will also be examined.