Hybrid modelling of multi-layered geological structure under seismic excitation

Abstract

This paper deals with seismic response evaluation of a finite multilayered geological structure with non-parallel boundaries rested on semi-infinite elastic half-plane subjected to transient seismic wave. The hybrid modelling approach is applied. It is based on the decomposition of the whole domain under consideration into two subregions: a finite-sized near-field zone and the open semi-infinite far-field region. The near-field range is presented by a finite geological profile, which is heterogeneous due to non-parallel layering. The far-field region is semi-infinite elastic isotropic homogeneous medium where the finite layered structure is located. An efficient 2D hybrid computational tool based on the boundary element method (BEM) for the far-field zone and the finite element method (FEM) for the finite layered domain is developed and verified in frequency domain. The BEM model of the seismically active far-field zone is inserted as a macro-finite element (MFE) in the FEM commercial program ANSYS. The hybrid model is of the FEM hosted type, where the boundary element domain (BED) is converted into macro-finite element, the nodal forces along the interface between two zones are expressed through the BED nodal tractions and the entire BEM formulation is converted to FEM-like approach. This hybrid model is applied for modelling of a real geological profile of the main wall of the “Liulyakovitsa” tailing pond, near Panagyurishte town, Bulgaria. Simulation results are given in the form of free surface synthetic seismograms stemming from the real seismic signals recorded at bedrock so as to establish the tailing pond’s seismic response.