Dynamic analysis of soil-rock mixtures based on improved 3-D DDA-SPH method

Abstract

Soil-rock mixtures (SRMs) are common in nature and are characterized by strong heterogeneity due to the coexistence of soil and irregular rock blocks. Understanding their complex deformation and failure mechanisms under dynamic conditions remains a major challenge. In this study, a powerful numerical approach is proposed based on the improved three-dimensional coupled Discontinuous Deformation Analysis and Smoothed Particle Hydrodynamics (3-D DDA-SPH) method for analyzing the behavior of SRM slopes in three-dimensional conditions. Key improvements include a face-based multi-shell contact detection algorithm for fast neighbor boundary searching, an advanced contact force model that distinguishes particle-to-face, particle-to-edge, and particle-to-vertex interactions between DDA blocks and SPH particles, and the implementation of a nonlinear softening constitutive model within the SPH module to better capture soil behavior under large deformation. The improved 3-D DDA-SPH method is well validated through theoretical and experimental tests and is applied to the investigation of the effect of block sphericity on the SRM slope failure mechanism and dynamic behavior. The results demonstrate that irregular blocks with low sphericity significantly restrict deformation, localize failure zones, and reduce sliding volumes, whereas spherical blocks have a limited resistance. Moreover, high-sphericity blocks within the SRM exhibit increased rotational motion during landslide events, contributing to a more dispersed deposition pattern compared to blocks with lower sphericity. These findings provide valuable insights into SRM slope behavior and offer practical implications for slope stability assessment and the design of landslide mitigation strategies. The proposed method offers a robust tool for analyzing mixture geomaterials in geotechnical engineering.