An innovative computer code for 1D seismic response analysis including shear strength of soils

Abstract

The development of a soil shear rupture during an earthquake can occur along unstable slopes and at the foundation level, for sliding failure mechanisms. This singularity in the seismic wave propagation is not implemented in the common codes for one-dimensional seismic response analysis, usually including linear equivalent soil models. Instead, the code developed in this study was conceived, addressed and optimised to reliably model both the ‘transient’ seismic response (‘stick’ mode) and the permanent deformation mechanisms accounting for the coupled effects of deformability and strength (‘slip’ mode). The code models the soil profile as a system of consistent lumped masses, connected by viscous dampers and springs with hysteretic non-linear behaviour. The viscous damping matrix is defined according to the Rayleigh formulation. The non-linear hysteretic soil response is described by the MKZ model and modified Masing rules. The shear failure is modelled through plastic sliders activating when the limit shear strength is reached. The code is applied to model the behaviour of an earth dam and a natural slope that have undergone significant displacements during strong-motion earthquakes; the results are compared with the observations and those obtained by uncoupling the seismic response from the displacement analysis by the rigid sliding block model.