Mechanism of Secondary Lining Cracking and its Simulation for the Dugongling Tunnel

A large amount of lining cracks, pavement uplift and cable trench overturning occurred during the operation of the Dugongling tunnel, which finally led to the closure of the whole line. The study on the lining cracking mechanism is very important to ensure that the tunnel opens again early. First, the actual cracks of the lining were investigated in the field. According to the geological data, the expansion and softening of the surrounding rock is likely to be the main cause of lining cracking. To verify this inference, a corresponding research program was drawn up. Then, representative sections were selected and the back-analysis method was used to simulate the cracking characteristics of the lining. Based on the simulation results, the cracking mechanisms were studied. The research showed that the increased water content caused the expansion and softening of the surrounding rock, increased the uneven loading on the lining structure, and, finally, led to lining cracking and pavement uplift. Based on the cracking mechanism, progressive enhancement schemes were proposed for each section. The research results of this paper can provide a reference for the design and construction of this project and similar projects.