Abstract:

Based on the field data of Metro Line 1 of a certain city in soft soil area, the disease state and crack pattern of the whole line and a typical section in soft soil area were statistically analyzed. Statistical results show that the distribution of the cracks is demonstrably related to the convergence displacement of the tunnel. And longitudinal crack turns to be the main disease in metro section, while it is densely distributed on the tunnel vault and its distribution regularity is related to the rotation angle of the ring. On this basis, in the way of nonlinear numerical analysis method of damage mechanics, a layer-structure numerical model was established in order to analyze the adverse effects of weak ground conditions on tunnel rings. The segment was given the smeared crack model and was embedded with simplified reinforcement grid elements, while the longitudinal joint was simulated by the gap contact model in order to consider the joint opening. The cracking characteristic of the segment and its influencing factors were illustrated from calculation results. The results show that: 1) when the elastic modulus and lateral pressure coefficient of surrounding soil increase, the tunnel damage area rises significantly under in-situ stress condition. 2) As the burial depth increases, the current crack zone and the predicted crack zone depth further expand on the original basis, resulting in an increase in overall crack rate. 3) The cause of the crack pattern on the tunnel vault revealed by the parameter analysis is the position of the key segment.

Key words: TBM tunnel, disease, measurement analysis, segment crack, structural nonlinear