Abstract:  To avoid the limit of grid distortion when using a finite element method to simulate large deformation, a twophase singlepoint material point method is employed to examine the evolution mechanism of watersoil gushing around shield tunnel and its influence laws on the hydromechanical behavior of soil. The proposed method is verified using a sand leakage model experiment and then applied in an engineering case. Based on the monitoring data, the development of ground settlement, the evolution of stress field, and pore pressure field in soil are analyzed in this study. With respect to watersoil gushing, the displacement field of the surrounding soil can be classified into three zones: flow, disturbed, and stationary zones. The development of the flow zone can help determine the influence of watersoil gushing. The process of watersoil gushing can be classified into three stages: initial, rapid developing, and stable stages. The influence of watersoil gushing on surrounding soil can be minimized by its timely detection and implementation of appropriate control measures at the initial stage. Finally, the parameter analysis results reveal that: the higher the gushing point location, the faster is the sand loss rate and the greater is the impact on the soil layers in the rapid developing stage; the lower the gushing point location, the larger is the final flow zone after the stable stage and the greater is the influence on the soil stress field.

Key words: material point method, shield tunnel, watersoil gushing, large deformation of soil