Three-Dimensional Stability of Unsaturated Excavation Slopes Under Different Seepage Conditions: A Case Study

Three-dimensional stability analysis of soil slopes remains a hot topic in the field of geotechnical engineering. Considering the fluid–solid coupling effect, this study performs a number of numerical analyses on the stability of a 3D excavation slope located in the Wuxi Taihu Tunnel, China. Three typical cases of the issued slope are investigated, i.e., the slope at the initial state, with the water-stop curtain, and with both the water-stop curtain and concrete-sprayed layer. The shear strength reduction method was adopted to determine the factor of safety (FOS) of the slope. The distributions of pore pressures and wetting lines, the horizontal and vertical displacements, and the critical slip surface are presented. The results indicate that the water-stop curtain can prevent the groundwater seepage effectively. The water-stop curtain and concrete-sprayed layer are effective in restraining the slope deformation, altering the critical slip surface, and improving the slope safety.