Numerical simulation investigation on the seepage characteristics of aperture dilated rough single fracture under two-way hydro-mechanical coupling effect

The interaction between fluid flow within fracture and fracture geometry has an essential influence on fracture seepage characteristics, but is often neglected in conventional simulation and laboratory tests, and we often refer to this interaction as "two-way hydro-mechanical (HM) coupling". In this study, a novel 3D rough single fracture HM coupled seepage flow model is established, which realizes the two-way coupling between the fluid flow within fracture and the change of fracture aperture. The seepage characteristics of a series of 3D fractures with different surface roughness and stiffness are studied under the two-way HM coupling. The variation of HM coupling strength and fluid inertia effects strength and their influencing factors were investigated. The results show that the HM coupling effect in the fracture increases the mechanical aperture of the fracture, slows down the growth rate of the fluid inertia effects, reduces the nonlinearity of the flow, and increases the flow rate, and all these effects are positively correlated with the pressure gradient. Roughness, stiffness and pressure gradient will all affect the strength of the HM coupling in the fracture, and the latter two have a more significant and critical impact. The research results are helpful to more comprehensively and accurately predict the permeability characteristics of fractures and the fluid flow inside them.