Numerical implication of water–soil leakage induced by longitudinal tunnel segment dislocation opening in saturated strata

Water–soil leakage due to the longitudinal dislocation opening of tunnel segments in high-permeable soil strata is crucial for ensuring the longevity of underground tunnel infrastructures. This research delves into this complex phenomenon employing coupled computational fluid dynamics (CFD), discrete element method (DEM), and finite element method (FEM), considering varied tunnel buried depths and dislocation opening sizes. Two critical areas susceptible to water–soil leakage have been identified, including an ‘ellipsoid’ shaped area at the tunnel top and a soil sliding area perpendicular to the tunneling direction. With a narrow segment opening (3 d 50 ), the fine loss remains below 2% across various buried depths, whereas it escalates to 7.4%–30% with increasing buried depth under a slightly wider opening (3.8 d 50 ). The proposed three-dimensional (3D) ellipsoid model is used to delineate the leakage region and quantify over 98% ground soil loss due to dislocation opening. Furthermore, the research reveals that soil sliding induced by water–soil leakage significantly decreases the structural shear stress on the waists and inverts of the tunnel segment, while the soil arching at the top of the tunnel would mitigate the stress release, particularly at the lower dislocated tunnel segment.