BEM-FEM Coupling in the Time-Domain for Soil-Tunnel Interaction

Abstract

The aim of this work is to develop, verify and implement for the purposes of numerical simulation studies an efficient, hybrid time-dependent computational technique based on the boundary element method (BEM) and the finite element method (FEM) for evaluation of the seismic response of a complex soil-structure systems. This way, it is possible to take into consideration the entire seismic wave path from the transient seismic source, through stratified with non-parallel layers half-plane, up to the level of a lined tunnel with complex construction. The hybrid numerical scheme is realized via the direct BEM based on the full space elastodynamic fundamental solutions in either Laplace or Fourier domains; Lubich Operational Quadrature in order to obtain time-dependent stiffness matrix and load vector of the seismically active far-field zone; conventional FEM for describing the near-field soil profile together with a lined tunnel; and finally insertion of the BEM model as a macro-finite element in the FEM commercial software package ANSYS. The accuracy of this approach in the ensuing verification study is discussed. The presented numerical simulations reveal the complex character of the seismic field in an inhomogeneous and heterogeneous geological medium containing additionally an underground structure.