(1. The College of Architecture and, Civil Engineering, Beijing University of Technology, Beijing 100124, China; 2. Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100124, China; 3. Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China)
Abstract：Understanding hydro-mechanical interactions in geological media is fundamental for addressing critical challenges in geohazard prediction, resource extraction, and crustal dynamics. While the discrete element method (DEM) coupled with fluid flow solvers has shown promise in these domains, conventional explicit coupling schemes suffer from overly restrictive time-step constraints and excessive computational costs when modeling fluid-fracture interactions. This study presents an innovative implicit coupling framework that synergistically combines the finite volume method (FVM) for solving Stokes flow equations with DEM-based mechanical analysis using two-dimensional particle flow code (PFC2D). The hybrid approach features: (1) An FVM implementation in Python for efficient implicit solution of fluid pressure fields; (2) DEM-based mechanical response calculation; and (3) Tight coupling through iterative information exchange between fluid and solid domains. Three benchmark simulations validate the proposed methodology and its high efficiency: (1) Steady-state seepage analysis demonstrates linear pore pressure distribution along flow paths and Darcy-law compliant flow rates proportional to hydraulic gradients; (2) Transient consolidation modeling of soil pillars reveals excellent agreement with Terzaghis analytical solution across temporal evolution of pore pressure dissipation; (3) Hydraulic fracture propagation simulations capture both viscosity-dominated and toughness-dominated regimes consistent with KGD model predictions, while uniquely resolving fracture-induced pressure oscillations and rock vibration dynamics; (4) The calculation time step size in the three cases is 3–4 orders of magnitude larger than that of the original method, leading to a significant improvement in computational efficiency. The demonstrated capabilities in modeling coupled flow-deformation-fracture processes position this framework as a powerful computational tool for geological engineering studies.
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2026, Vol. 45 
