Water Erosion and Extension of Ground Fissures in Weihe Basin Based on DEM-CFD Coupled Modeling

The Weihe Basin is one of the regions with the highest concentrations of ground fissure development and the most serious disasters in China. Hidden ground fissures are formed in the shallow soil layer due to preexisting fissures generated by tectonism, hidden ground fissures suddenly exposed to the surface after heavy rainfall. Because the details of the water erosion process cannot be replicated by geological survey methods, the erosion and extension mechanism has not fully developed and the discontinuous medium numerical simulation method is well suited for simulating large deformations and facilitates a microscopic perspective in elucidating the underlying causal mechanisms. This paper deploys the discrete element method (DEM)-computational fluid dynamics (CFD) fluid-solid coupled method modeling the growth process of hidden fissures containing different soil types (sand and clay) under heavy rainfall, revealing a mechanism for the development of hidden fissures into surface fissures. The findings include: (1) the emergence process of hidden fissures into surface fissures under heavy rainfall can be summarized into four stages: subsurface erosion into hidden holes, traction into arches, collapse into sinkholes, and horizontal extension; (2) the emergence process of clay is slower than that of sand due to the constraint of cohesion; (3) the shape of the bottom seepage point affects the fissure emergence process, which is an important factor in the macroscopic performance of the exposed surface fissures. The intuitive and reproducible DEM-CFD coupled modeling used in this paper possesses important reference value for the study and prevention of water erosion ground fissures.