Finite Element Seismic Analysis of Soil–Tunnel Interactions in Clay Soils

Abstract

Seismic waves propagate from bedrock through the soil layers and during this propagation they pass different layers of soil and rock until they reach the soil surface. These waves can be amplified or damped by the soil layers. Underground structures response, like tunnels, is related to a number of factors such as soil type and earthquake frequency. In this paper the simulation of the models is done in two-dimensional plain strain system with finite element mesh generation which consists of soil–tunnel using frequency spectrum analysis. All analyses consist of three actual ground motion records with low, intermediate and high-frequency content. Two different clay soils (Normally or Lightly Over-Consolidate Clay and Heavily Over-Consolidate Clay) have been used in free field and models consist of cylindrical tunnel. In this study, the results of both free field (models without structure) and soil–tunnel analysis have been compared to show the effect of the tunnel on responses. Effect of soil–tunnel interaction in all earthquakes with different frequency content on-site response, amplification, acceleration response and stress and strain propagation in the tunnel’s perimeter are discussed. Based on the results of the analysis, acceleration frequency at different depths of models had different characteristics. Both clay soils amplified seismic waves on the soil surface in free filled models and the soil–structure interaction effects on the tunnel dynamic responses.