Impact of Shear Strength Degradation on Raft Foundation Performance in Clay Shale

The construction of structures on clay shale soils presents significant challenges due to the soils' propensity for water absorption and associated volumetric changes. These problematic soils are characterized by weak bond structures and expansive clay minerals that can lead to severe structural damage and foundation instability. This study investigates the performance of raft foundations under varying conditions of shear strength degradation and different thicknesses of degraded clay shale layers. The study employs numerical simulations using the finite element software PLAXIS 3D, which allows the detailed modeling of soil-structure interactions. Various scenarios were analyzed, considering shear strength degradation and clay shale thickness variations ranging from 0.5 m to 2.5 m. The findings indicate a clear trend of decreasing safety factors and increasing settlement with both the degradation of shear strength and the increased thickness of the degraded clay shale layer. These results emphasize the critical impact of soil degradation on foundation performance and highlight the necessity for rigorous soil assessments and the implementation of mitigation strategies to ensure long-term structural stability. The study's insights and recommendations contribute to advancing geotechnical engineering practices, thus promoting safer and more resilient foundations in challenging soil conditions.