Numerical study on failure propagation between two closely spaced tunnels

Abstract

An increasing number of engineering accidents have shown that the failure of a tunnel can propagate to a neighbouring tunnel. However, due to the complex interaction between the failed tunnel structure and the soil medium, the mechanism by which the failure is propagated between two closely spaced tunnels remains unclear. In this study, the coupled Eulerian-Lagrangian (CEL) modelling technique was adopted to investigate the influence of a failed tunnel (FT) on an adjacent tunnel, which was termed an "influenced tunnel" (IT). The safety of the IT was analysed in detail under different circumstances, such as different failure positions of the FT, different failure degrees of the FT, and different spatial relationships between the two tunnels. The simulation results indicated that the most adverse case may occur when the two tunnels are arranged as offsets and the IT is the upper tunnel. Under this circumstance, significant shear deformation may occur in IT because IT is located at the shear band of the FT.