Simulating the water-soil leakage induced deformation around the shield tunnel with material point method

Water-soil leakage can induce large soil deformation around the urban metro shield tunnel, and potentially threaten the safety of the metro system operation. It is time consuming and operationally difficult to conduct experiment to test this leakage process in lab condition. Numerical methods were adopted in many previous studies to investigate this complex process: finite element method (FEM), discrete element method (DEM), and CFD-DEM coupled method. However, none of these numerical methods can simulate the tunnel scale leakage-induced soil failure around the shield tunnel. Therefore, the material point method (MPM) is adopted in this study, which has been widely used to deal with large deformation geotechnical problems. A case study of the incident happened in Shanghai Metro Line 18 is studied to simulate the large quantities of water and soil inrush into the tunnel due to the construction errors in the freezing process. The performance of surrounding soil caused by leakage process, such as the ground settlement, the mass and the velocity of soil leakage, the soil displacement field, the soil stress filed and the pore pressure field, are then carefully calculated by conducting a reasonable numerical simulation. The evolution law of water-soil leakage process sensitivity is analyzed to suggest possible countermeasures and guidance for preventing such tunnel failure in the future.