Experimental and numerical simulation for shear failure mechanism of silty clay–structure interface

The shear phenomenon between soil and foundation structure is common in foundation engineering. The change in the water content of stratum affects the shear behavior of soil and structure inevitably, especially in the region of cohesive soil with complex hydro-physical properties. In this paper, the silty clay in the Songnen Plain was used as a case study to reveal the shear failure mechanism of silty clay–structure interface under different water contents from multiple scales. First, the macroscopic mechanical characteristics were investigated by direct shear test and particle-image-velocimetry technology. To further explore the mesoscopic evolution law, this study proposed a novel FDM-DMDEM (Finite Difference Method–Determining Meso-parameter Discrete Element Method). This method enables direct calculation and assignment of meso-parameters required for the numerical model based on unsaturated soil theory, completely circumventing the laborious and subjective inverse calibration process inherent in conventional DEM. In this study, a 3D numerical model was established by using this coupling method and a parametric analysis was carried out. The results demonstrated that the meso-structure failure of silty clay within a certain range from the interface produced plastic deformation to form shear bands. Failure has two forms, namely, shear failure inside the shear band and shear failure outside the shear band. The increase in water content weakened the bonding force between particles, so that developing shear stress outside the shear band was difficult, resulting in typical shear failure inside the shear band. These findings could provide certain design references for the construction of foundation engineering in the Songnen Plain area.