New approach for assessing long-term stability of tunnel and remedial work

In this paper, a finite element analysis is conducted to investigate the long-tem stability of a tunnel excavated in a shattered zone. The analysis is based on an elasto-viscoplastic model with strain hardening and strain softening. The purpose of the present research is to investigate the mechanism of the long-term stability of the tunnel due to the time-dependent behavior of the surrounding ground. Particular attention is paid to the redistribution of stress within the ground due to strain softening and the time-dependent behavior. The constitutive model adopted in the finite element analysis not only can describe the strain-softening behavior but also such time-dependent behavior as creep failure, strain-rate dependency, and stress relaxation. The material parameters involved in the model are determined through a series of laboratory tests. From the analysis, it is possible to provide a new approach for assessing the long-term stability of tunnels and the effectiveness of the remedial work performed on the tunnels