Numerical Simulation Study of Stratum Subsidence Induced by Sand Leakage in Tunnel Lining Based on Particle Flow Software

To obtain the dynamic development process of the stratum subsidence of sandy soil layer induced by the cracks of the tunnel lining, and the formation and dynamic change of soil arch during the process of subsidence, a sily-type sand gushing model was established by the particle flow software (PFC2D). The parameters of sandy soil particles were calibrated by biaxial compression test. Furthermore, the flow pattern of sand in the process of stratum subsidence caused by sand leakage induced by cracks in the tunnel lining, the change of the inter-particle force chain during the formation of the soil arch were simulated. It was shown that when the stratum subsidence induced by the cracks of the tunnel lining occurred, the development process of sand collapse was a dynamic process accompanied by the formation and destruction of soil arches. And the ratio of crack width of lining to particle diameter and the internal friction angle between the sand were important factors of sand collapse disaster in the process of stratum subsidence. The necessary conditions for sand collapse were that the ratio of crack width of lining to particle diameter reached 5.1 and the friction coefficient reached 0.6. With the increase of the width of the sand leakage crack, a stable contact force arch was more and more difficult to be formed.