Mechanical behavior of secondary tunnel lining with longitudinal crack

Concrete cracking is prone to occur in secondary linings during tunnel operation. In this article, the Chongqing highway tunnels, China, was taken as an example to study this issue. Firstly, a field investigation was conducted to reveal the cracking situations of these highway tunnels. Then, similarity model tests were adopted to analyze the cracking features of intact lining and cracked lining. Finally, a new shell-spring numerical model was put forward to investigate the safety of cracked lining. The results reveal that: (1) The influence of cracks on inner force along tunnel perimeter shows distinct zoning effect, tensile effect and asymmetric effect; (2) The lining undergoes progressive failure process with four evident period, that is, elastically deformed period, initial damage period, ultimate limit period and instability period, and the feature of failure brittleness for lining with crack at tensile zone is strongest; (3) The pre-existing crack at tensile zone develops toward the outside surface and finally penetrates through the cracked section at the failure stage; (4) Within the influencing area of the crack, the inner force decreases with the increase in its damage degree. In addition, the damage degree of crack and the equivalent rock depth are the two main factors influencing the safety of lining.