Abstract: This study develops a new method for in-depth analysis of the deformation mechanism during the construction and operation of rockfill dams, using a hierarchical multiscale computational approach that couples the Material Point Method (MPM) with the Discrete Element Method (DEM). As a critical type of structure in hydraulic engineering, a rockfill dam features deformation that involves complicated interaction between its particle-scale behavior and the overall response of its body; Understanding the mechanism of its micromechanical deformation is crucial for safety assessment, design, and construction. Aiming at a comprehensive capture of the deformation characteristics of a rockfill dam, we first discretize its body into multiple representative volume elements (RVEs), then simulate its behavior at the particle scale and capture variations in local stress and particle contact force in its body. For the different stages of dam construction, analysis of the spatial distribution patterns of stress and deformation reveals a significant impact of reservoir water level changes on its deviatoric stress and particle contact behavior. In the completion stage, the maximum settlement feature points exhibit significant contact anisotropy, with denser force chains in the vertical direction, indicating a higher efficiency of stress transfer in this direction. As the water level rises, significant changes occur in the contact state and force chain distribution in the dam body, resulting in an increased horizontal anisotropy at the maximum settlement point, thereby enhancing the dam's resistance to water pressure. During the normal reservoir stage, particle contact on the upstream side of the main rockfill zone weakens, and the coordination number decreases. The multiscale method developed in this study overcomes the limitations of traditional analytical approaches, providing a new quantitative framework for the deformation prediction, long-term stability evaluation, and design optimization of rockfill dams.

Key words: hydraulic engineering, rockfill dam, granular material, multiscale simulation, deformation prediction