Reliability of Soil Sublayers Under Earthquake Excitation

A hysteretic model is formulated for a multi-layer subsoil subjected to horizontal earthquake shear waves (SH-waves). For each layer a modified Bouc-Wen model is used, relating the increments of the hysteretic shear stress to increments of the shear strain of the layer. Liquefaction is considered as failure event. Cyclic triaxial tests indicate that strength and stiffness of a layer deteriorate proportionally. Further, that liquefaction takes place when the accumulated mechanical energy dissipated per unit volume exceeds a critical value. This quantity is then introduced as a damage indicator for each layer. The horizontal earthquake acceleration process at bedrock level is modelled as a non-stationary white noise, filtered through a time-invariant linear second order filter.