Study on Seismic Response and Damping Performance of Tunnels with Double Shock Absorption Layer

Shock absorption layer is an effective measure to decrease damage of tunnels under earthquake. According to previous work, the smaller stiffness of damping material, the better damping effect of the tunnel. In order to meet the actual engineering requirements, the shock absorption layer is applied to the upper part of tunnels (not including the invert), which is called a local shock absorption layer. This study is to analyze the damping effect of different types of local shock absorption layers based on the dynamic nonlinear time-history numerical analysis. Six real ground motions with different dominant frequencies are selected, their peak ground accelerations (PGA) are set to 0.2 g, 0.4 g, 0.6 g, and 0.8 g, respectively. The damage index and total dissipated energy of secondary lining, and equivalent plastic strain of surrounding rock are used as indicators to reflect the damping performance of the local shock absorption layer. Numerical results highlight that the damping performance with double local shock absorption layer is the best, and the damping performance of shock absorption layer under large earthquake is better than that under small earthquake.