Numerical Investigation of Coupled Soil-Structure Interaction and Progressive Strength Degradation in Pile-Supported Retaining Wall

This research conducts a detailed forensic investigation of the Daya Bay Binhe Road slope failure in Huizhou, China, utilizing 3D Finite Element Modeling in Abaqus to capture complex soil-structure interactions. By employing the Dafalias & Herrmann bounding surface elastoplastic model, the study quantifies a drastic ~80% reduction in cohesion within critical stratified layers—dropping from 18 to 10 kPa in Layer 2 and 8 to 2 kPa in Layer 3—as the primary trigger for instability. The numerical data reveals a maximum settlement of 1.947 meters, which is significantly higher than the calculated 7 mm allowable limit for the pile groups. Analysis confirms that the structural collapse was driven by differential settlement and localized stress redistribution across heterogeneous soil layers rather than uniform total settlement. To address these vulnerabilities, the study proposes and verifies two optimized solutions: extending pile embedment into the competent 4th soil layer or providing a concrete base at the foundation level to bridge shear failure planes.