Study on the mechanism of EPWP dissipation at the joints of shield tunnel in liquefiable strata during seismic events

The segment joints of a shield tunnel are susceptible to deformation and leakage during seismic events. In liquefiable strata, opened joints can form seepage channels, which accelerate the dissipation of pore pressure. This study explores the interaction mechanism between tunnel structure with significant segment joints deformation and liquefiable strata under earthquakes, considering the multi-joint characteristics of a shield tunnel. First, shaking table tests were conducted to examine the dynamic characteristics of a tunnel structure with multiple joints in liquefiable strata. Based on the measured data from these tests, an optimal marginal distribution was selected from four different distribution types based on the measured values of the test results. Subsequently, a two-dimensional probability distribution model of dynamic response factors was established using Copula theory to analyse the relationship between excess pore water pressure (EPWP) dissipation and tunnel radial deformation. The correlation between EPWP dissipation and tunnel radial deformation with joints opening in the liquefiable strata was clarified. The results reveal significant differences in EPWP dissipation across different positions of the tunnel. The Gaussian Copula method effectively fits the EPWP distribution and tunnel radial deformation, indicating a positive correlation between EPWP dissipation and joints deformation. The formation of new seepage channels at the tunnel joints exacerbates EPWP dissipation. The developed probability distribution model provides a new approach for studying the dynamic response between tunnel and liquefiable soil.