Computational fluid dynamics–finite discrete element method simulations of saturated granular material under seismic excitation

This study develops a novel and efficient computational fluid dynamics–finite discrete element method (CFD-FDEM) framework to simulate the dynamic response of saturated granular materials subjected to seismic excitation. A key innovation is the efficient coupling of fluid and solid phases using the immersed boundary method (IBM), enabling accurate resolution of fluid–solid interactions in dynamic, multiphase systems. To ensure scalability, the framework incorporates a parallelized message passing interface (MPI) architecture with optimized contact detection and a coarse-grained message delivery scheme, which significantly reduces interprocess communication and enhances overall computational performance. According to the particle response, base vibrations are classified as either destructive or nondestructive, and the corresponding spatial–temporal evolution of pore water pressure is systematically analyzed for both cases. In nondestructive cases, particle displacements remain limited, and the system largely retains its initial structure, with only minor pore water pressure variations. In contrast, destructive vibration induces a three-stage particle response—pre-damage, damage, and post-damage stages—accompanied by pronounced cyclic fluctuations in pore pressure. The spatial–temporal evolution of pore pressure under both regimes is analyzed to reveal the underlying fluid–particle coupling mechanisms. The proposed CFD-FDEM framework provides a robust and scalable tool for investigating seismic responses in saturated granular systems, offering new insights into failure mechanisms and pore pressure dynamics.