Numerical study on the mechanism of fluid flow through single rough fractures with different JRC

Abstract

The permeability theory of fractured rock mass has a wide range of engineering applications. The surface roughness and structure tortuosity have a significant effect on the character of fluid flow through the fracture. Based on the standard fracture curves with different JRC values given by Barton (1977), a rough single fracture model is constructed. A detailed mechanism study on the effect of roughness and tortuosity on fluid flow is carried out on the single fracture model. A code for simulating the flow in the fractures based on the lattice Boltzmann method was programmed and verified. Using this code, numerical simulations are performed on single fracture models with different JRC values and apertures. Physical properties like the velocity field of the flow are observed and analyzed. Comparing the simulation results with the tortuosity modified the cubic law of single fracture flow (LCL), it is found that the cubic law prediction has a certain deviation on the flow rate. The analysis emphasizes that in the single rough fracture, two factors of tortuosity and roughness act simultaneously on the penetration, and these two factors are coupled that they can transform from one to the other as the aperture changes. Therefore, it is necessary to consider both the tortuosity and the rough effect and implement the two factors to modify the local cubic law for single fracture permeability. The modified model shows the result which is relatively more accurate in predicting the flux through rough single fractures. It is convinced that the research is engineering valuable.