Abstract: Developed from the modified scale boundary finite element method and continued fraction solution, the high-order doubly asymptotic transmitting boundary can realize time localization and generate a stiffness matrix that converges rapidly to the exact solution over the whole frequency range, thereby achieving a high accuracy and good efficiency. This paper applies such a transmitting boundary to the propagation of elastic waves across complicated layered soil, and develops a time-domain coupled model by combining with FEM to study the dynamic responses of a tunnel-layered soil system. This coupled model divides the domain into a near field and a far field by a transmitting boundary, and calculates both separately using a FEM model and a high-order doubly asymptotic transmitting boundary method. Results of numerical examples demonstrate that the solutions are stable and agree well with those of the extended mesh method, achieving a good balance between accuracy and efficiency. And it is also applicable to long-time seismic response analysis of tunnel-layered soil interaction. Thus, the coupled model would provide a new approach for seismic analysis of tunnel-layered soil interaction and should be developed further for engineering application.

Key words: time-domain analysis, transmitting boundary, layered soil, scaled boundary finite element method, continued fraction solution