Coupled FEM/SBFEM investigation on the characteristic analysis of seismic motions of a trapezoidal canyon in a layered half-space

Abstract

Layered topographies and geologies are known to have considerable effects on the spatially variable seismic motions scattered by a canyon in a layered half-space. In this study, based on a substructure replacement technique, a coupled finite element method and scaled boundary finite element method based on scaling splicing lines (hereafter referred to as coupled FEM/SBFEM) is developed for a scattering field analysis, considering the effect of the layered topographical characteristics. The near field is modelled using the finite element method (FEM), and the far field is modelled using an improved scaled boundary finite element method, which can model the radiation damping of a layered half-space precisely. In the modified version of SBFEM, a novel dimensionless frequency is proposed to facilitate obtaining the time-domain response efficiently using a fast Fourier transformation. Several examples are investigated to demonstrate the versatility and validity of the proposed method. Parametric studies are performed to investigate the characteristics of the ground motions of a trapezoidal canyon in a layered half-space in the frequency and time domains (where the ground motions significantly differ from those of a uniform half-space), and to investigate the effects on ground motions caused by the soil layer thickness, burial depth, and impedance ratio.