Numerical Forensic Analysis of Brittle Failure of Cantilever Sheet Pile Walls due to Point Infiltration in Soft Clay

The collapse of cantilevered sheet pile walls on very soft clay layers in urban areas is often exacerbated by overlooked anthropogenic factors, such as drainage system leaks. Conventional geotechnical analysis is generally biased toward short-term undrained parameters ( ) without considering the hazard of continuous saturation. This study aims to conduct an investigation using a 2D Finite Element Method (FEM) to evaluate the impact of drainage channel infiltration on the transition of soil hydromechanical behavior from the undrained to the drained phase based on a field case study. The analysis results indicate that seepage flow reduces the soil’s effective stress, lowering the Safety Factor (SF) from the existing critical limit of 1.07 and contributing to a simulated soil body collapse. Furthermore, a potential change in the landslide mechanisms was numerically observed; from a ductile global rotational failure (deformation 0.244 m) to a brittle failure and strain localization at the pinning depth (deformation 0.035 m). The simulated loss of soil shear strength, coupled with lateral hydrostatic pressure, contributed to structural over-stressing, marked by a surge in bending moment values exceeding 320% (from 129.0 to 421.2 kN·m/m) and a shift of the critical point toward the center of the span. As a practical implication, this study recommends the integration of proactive hydrological mitigation measures and the reactive installation of weep holes to prevent the failure of geotechnical infrastructure due to anthropogenic factors.