Research on the Leakage Effect of Shield Tunnels in Water-Rich Silty Clay Strata Based on On-Site Investigation and Numerical Simulation

Based on a metro project in Hangzhou, combined with the investigation of on-site seepage and leakage problems and finite element numerical simulation, the influence of local seepage and leakage in shield tunnels in water-rich silty clay strata on stratum settlement and lining structure deformation was studied. During the simulation process, two working conditions, namely leakage at the joint of the segment and local damage leakage, were, respectively, set up to analyze the distribution of pore water pressure, the development characteristics of stratum settlement and the response of the lining structure. The results show that the pore water pressure near the leakage area is significantly reduced. The pore pressure at the joint of the segment and the local leakage position is reduced by 81.22% and 76.88%, respectively, compared with the hydrostatic pressure at the same burial depth, and the reduction at the bottom of the model is 11.45% and 6.46%, respectively. Under different working conditions, the settlement rates all increased first and then tended to stabilize. The maximum surface settlements were 91 mm and 32 mm, respectively, and the former exceeded the control value. The surface settlement of local leakage is distributed in a concave pattern, and the peak settlement is located directly above the leakage point. The lining structure deforms significantly in both the upper and lower directions, both shifting downward towards the stratum. The maximum displacement and deformation caused by the leakage at the joint of the segment reached 78.26 mm and 24.38 mm, respectively, with obvious over-limits. It is recommended to prioritize the sealing treatment of the leakage area at the joint. The research results can provide theoretical references for the control of water leakage and structural safety evaluation of shield tunnels in water-rich and weak strata.