Study on the Performance of Mountain Tunnel Against Mainshock-Aftershock based on Resilience Evaluation Framework

The mainshock-aftershock has a profound influence on the seismic resilience of tunnel. However, it is very dangerous to consider only the influence of the mainshock in the current seismic research of tunnel. This study is based on the resilience evaluation framework under multiple disturbances to study the resilience of the tunnel against mainshock-aftershock. A 3D finite element tunnel model was established based on Longdongzi tunnel. Eight real earthquakes were selected to construct the mainshock-aftershock sequence by the repeated method, and the seismic load was input into the tunnel model by the high-precision wave input method. The failure ratio of surrounding rock and transverse convergence of lining are used as performance indexes to evaluate the tunnel resilience. The results show that aftershocks can significantly amplify the damage of the tunnel structure damaged in the mainshock, and the equivalent plastic strain of surrounding rock after aftershocks can increase by 253% at most compared with that after the mainshock, and the lining cracks will expand from microcracks to through cracks and eventually lead to the collapse of the tunnel lining end. The decreased value of resilience indicator DRe of tunnel surrounding rock after the aftershock is generally more than two times of that after the mainshock alone, and the highest DRe can reach 4.231 times. The resilience of each section of the lining structure experiences a certain loss after the main shock, and the loss of resilience is intensified after the aftershock. The resilience of the severely damaged section after the aftershock decreases remarkably, and the reduction range can reach about 50%. The hard surrounding rock can improve the resilience of the tunnel against the mainshock-aftershock, while the soft surrounding rock can cause the lining to deform greatly in the mainshock and continue to degrade in the aftershock.

Automated summary

This study investigates the resilience of tunnels against mainshock-aftershock using a resilience evaluation framework under multiple disturbances. The results demonstrate that aftershocks can greatly amplify the damage of tunnel structures caused by the mainshock, leading to increased plastic strain in the surrounding rock and the expansion of lining cracks. The resilience of the tunnel is reduced after both the mainshock and aftershock, with the severely damaged sections experiencing a significant decrease in resilience. Additionally, the hardness of the surrounding rock plays a role in the tunnel's resilience, with harder rock improving resilience.