Post-failure behavior of tunnel heading collapse by MPM simulation

Abstract

Tunnel collapse presents a serious threat to the safety of urban construction. The traditional approach adopted to assess this risk is to evaluate the factor of safety against failure. However, this analysis only determines on whether the tunnel will collapse or not, and does not provide information on the magnitude of the post-failure behavior (for example, catastrophic or progressive) if the tunnel collapse occurs. In this study, a meshless method based on the material point method (MPM) was used to investigate the post-failure behavior of tunnel heading collapse in two-dimensional plane-strain conditions. The capability and accuracy of MPM were verified by comparing the elicited results to centrifuge test data and to analytical solutions obtained from limit state methods. MPM simulations were conducted at different soil conditions (clay or sand) and profiles (homogenous or linear increasing strength) as well as at different tunnel geometries (i.e. tunnel depth and unlined length). The differences in the post-failure behavior and mechanisms are examined and reported.