Effect of group cavities on seismic response of adjacent overlapping shield tunnels and site soils

More and more adjacent, complicated underground structures will run across each other with the further exploitation and utilization of underground space, and hence, the seismic ability of underground structures will be influenced by the adjacent underground structures. Focused on the subway tunnels between Hongshang Square Station and Zhongnan Road Station on Wuhan rail transit lines No. 2 and 4, the relevant models for different numbers of tunnels and different tunnel net distances are established, and the seismic responses of tunnels and site soils influenced by group cavities effect are analyzed. The results show that: 1) the lower tunnel can cut off the transmission of seismic waves, and therefore, it can play the function of shock absorption; 2) the existence of the upper tunnel weakens the constraining effect of surrounding soils on the adjacent tunnel, and as a result, the seismic ability of the adjacent tunnel will be reduced; 3) the group cavities have little effect on the fundamental period of soils and acceleration magnification effect; and 4) the shallow overlying soil has a significant effect on the seismic ability of tunnels and acceleration magnification effect of site soils.