Nonlinear Anisotropic Seepage Characteristics and Energy Loss Study of Single Dislocated Rock Fracture

Natural, rough rock-mass fracture surfaces exhibit significant anisotropic properties. In addition, dislocation displacement and aperture variation have a significant impact on the complexity of the fracture seepage flow regime. Two-dimensional numerical models were developed using joint roughness coefficient (JRC) curves of a rough single fracture, and the effects of fracture roughness, aperture, dislocation displacement, and seepage direction on nonlinear seepage behavior were investigated. The changes in the Forchheimer law coefficients, critical Reynolds numbers, and energy conversion efficiencies of the fractures were analyzed. Local water head loss emerges as the predominant factor leading to a reduction in fracture permeability and variations in nonlinear seepage behavior. Moreover, higher JRC and dislocation displacements, combined with smaller aperture values, resulted in increased local water head loss and lower potential-kinetic energy conversion efficiency. Owing to the impact of local water head loss, significant differences in fracture permeability and energy conversion efficiency were observed, with changes occurring only in the seepage direction, particularly in the flow velocity and pattern distribution in the fracture expansion section. This discrepancy is even more pronounced in rough and narrow fractures. This suggests the development of a scalar parameter that can account for the anisotropic geometric properties of fracture surfaces in relation to seepage direction, as well as the use of energy conversion efficiency to describe fracture flow capacity.