Effect of Ground Loss on Seismic Performance of Shield Tunnel Using Discrete Element Method

The ground loss due to tunnel construction may change the stress filed near the tunnel and subsequently affect the seismic performance of tunnel. In this paper, the 2-dimensional model was established for dynamic analysis of shield tunnel by FISH-based programming, which was verified through numerical trial. Subsequently, the variation of initial stress filed and lining internal forces with ground loss was numerically simulated under static condition. Finally, the effect of ground loss on the seismic performance of shield tunnel was analyzed under various overburden depths of tunnel. The results indicate the following: (a) The artificial boundary can offer high accuracy for dynamic response analysis; (b) as the ground loss increase, the initial stress field near the tunnel varies from place to place, and the lining internal forces decrease. In addition, the lining internal forces increase with overburden depth; (c) when subjected to seismic action, the ground loss and overburden depth have great effect on the axial force in the lining. When the ground loss rate is larger than 2%, the axial force increases rapidly with increasing ground loss rate. When the overburden exceeds 18 m, the axial force is approximately 1.36 times the initial axial force; (d) the ground loss rate may be controlled to be around 2% by optimizing some parameters and thereby satisfy both the seismic safety and appropriate investment.