Numerical study on the dynamic response characteristics of liquefiable silty sand-rock composite strata - Tunnel system under the influence of the vibration of a shield cutter-head

Unlike the mechanism of earthquake or ocean wave loads, the dynamic response characteristics of the liquefiable strata under the influence of the vibrating loads of the cutter-head of shield tunneling in special strata are unique. This paper investigates the significance of the dynamic interaction between a large-diameter shield tunnel and the liquefiable saturated silty sand strata during the process of liquefaction-induced under the vibrating loads of a shield cutter-head. The coupled effective stress model-which is the Davidenkov nonlinear hysteresis model based on equivalent shear strain algorithm and irregular loading and unloading criterion combined with an incremental excess pore water pressure (EPWP) model coupled with shear-volume strain-is used to describe the stiffness degradation and characteristics of the rising EPWP during the process of liquefaction-induced. The material parameters of silty sand corresponding to the coupled effective stress model are calibrated based on the experimental data of samples obtained from dynamic triaxial shear test under cyclic loads. The numerical results indicate that the acceleration, the EPWP ratio (EPWPR), and displacement distribution of the liquefiable strata all match the influenced range of the vibrating loads, the influence of relative density and thickness of the sand strata. It is concluded that the vibrating loads of the shield machine tunneling in the silty sand-rock composite strata is unfavorable for the safety of the strata and tunnel, and grouting reinforcement should be carried out in a timely manner during construction.