Seismic response and deformation mechanism of near-fault deep tunnels in a strong earthquake area

The frequent occurrence of seismic activity in strong earthquake areas has led to the serious damage of deeply buried underground engineering structures. In the face of numerous and densely distributed fault fracture zones, deep tunnels in strong earthquake areas are required to cross the faults, causing large deformations and even destruction. However, the seismic failure law of the fault-crossing deep tunnels under strong earthquakes remains unclear. In this study, we selected the Xianglushan tunnel engineering as the subject to perform a series of shaking table tests and numerical simulation tests. The peak acceleration, peak strain and peak displacement were selected to indicate the seismic deformation characteristics, as well as the catastrophic mechanism from a near-fault to a fault-crossing deep tunnel under different influencing factors. The results reveal the fault dips to exert the most markedly amplification effect on peak acceleration, peak strain and peak displacement. With the fault dip increased, the amplifying effect of peak acceleration and peak strain continued to decrease, while the deformation values of the tunnel lining gradually increased. The fault width and relative distance also exerted an amplifying effect on parameters such as the peak strain and peak acceleration. As the fault widths increased, the peak acceleration and peak strain of the fault became more pronounced. Under the influence of the relative distance, the seismic response of the fault reached its maximum at a relative distance of 10 cm. This work determined the relative peak velocity and relative peak displacement of the deep tunnel during the seismic failure, and proposed a stability assessment method. The results provide a guidance for stability analysis and safety assessment of the deep underground tunnels in strong earthquake areas.

Automated summary

This study investigates the seismic failure mechanism of fault-crossing deep tunnels in strong earthquake areas through shaking table tests and numerical simulation tests. The results show that the fault dip has a significant amplification effect on peak acceleration, peak strain, and peak displacement. The fault width and relative distance also amplify parameters such as peak strain and peak acceleration. This research provides guidance for stability analysis and safety assessment of deep underground tunnels in strong earthquake areas.