Abstract
In this paper, the fluid flow through rough fractures was investigated via numerical simulation based on the lattice Boltzmann method (LBM). The accuracy of LBM was validated through the numerical simulation of the parallel plate model and the verification of the mass conservation of fluid flow through rough fracture. After that, the effect of roughness on fluid flow was numerically conducted, in which, the geometry of fractures was characterized by the joint roughness coefficient (JRC), fractal dimension (D) and standard deviation (σ). It was found that the JRC cannot reflect the realistic influence of roughness on the permeability of single fracture, in which, an increase in permeability with increasing JRC has been observed at the range of 8~12 and 14~16. The reason behind this was revealed through the calculation of the root mean square of the first derivative of profile (Z2), and an equation has been proposed to estimate the permeability based on the aperture and Z2 of the fracture. The numerical simulations were further conducted on fluid flow though synthetic fractures with a wide range of D and σ. In order to unify the parameter that characterizes the roughness, Z2 was obtained for each synthetic fracture, and the corresponding relationship between permeability, aperture and Z2 was analyzed. Meanwhile, it was found that the fluid flow behaves differently with different ranges of Z2 and the critical point was found to be Z2 = 0.5. Based on extensive study, it was concluded that Z2 is a generic parameter characterizing the roughness, and the proposed equation could be used to predict the permeability for fluid flow in fracture.
Highlights
The inherent fracture has a significant influence on the strength, deformation and seepage characteristics of rock mass
Rezaei Niya and Selvadurai [17] examined the relationship between the joint roughness coefficient (JRC) and permeability of a fracture through the numerical study based on COMSOL multiphysics
Based on the numerical study of fluid flow through fractures characterized by the joint roughness coefficient, fractal dimension and standard deviation, it was found that the lattice
Summary
The inherent fracture has a significant influence on the strength, deformation and seepage characteristics of rock mass. Rasouli and Hosseinian [10] developed a correlation to estimate the hydraulic parameters through a channel of combined JRC profiles under different minimum closures using a finite element method Further works include those by Xiong et al [11], who investigated the geometrical and hydraulic characteristic of rock fractures during shear through both experimental and numerical study; Indraratna et al [12], who proposed a 2D equivalent finite volume model that considers the hydraulic aperture distribution to solve the flow problem in deformable rough rock joints. Rezaei Niya and Selvadurai [17] examined the relationship between the joint roughness coefficient (JRC) and permeability of a fracture through the numerical study based on COMSOL multiphysics It is clear from the aforementioned studies that a deep understanding of fluid flow through rock fracture requires both an accurate geometry description and conceptual model that could characterize the flow behavior. The discussion and conclusion will be drawn at the end of this paper
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