Influence of degradation disease on tunnel stability based on a time-dependent constitutive model

The surrounding rock and lining of tunnels deteriorate with increasing operation time, which causes changes in the mechanical parameters of the lining material and then affects the stability of tunnels. According to the time degradation law of the lining proposed in this paper, the mechanical parameters of lining materials corresponding to different operation years of the tunnel can be obtained. Model tests of the lining without degradation and degradation for 10, 30, and 50 years were carried out. Based on the realistic failure process analysis (RFPA(2D)) system, the time-dependent failure constitutive model is introduced to simulate the degradation of the surrounding rock and lining. Based on the model test and numerical analysis, the influence of degradation on the mechanics and failure features of tunnel were studied. It was found that the degradation would impact the structural stress and the stability of the surrounding rock. The failure mode of the model and the loading stress were different with the degradation time. The longer the degradation time, the more serious the deformation of the vault, and the larger the damage area of the surrounding rock. The research results play an important theoretical guiding role in analysing the progressive failure process of the surrounding rock and lining and have great value in engineering applications for reinforcing and treating tunnel defects.