A comparative study on the influences of fracture intersections on the prediction of rock mass permeability

Geometric predictive methods are efficient for determining the permeability of fractured rock masses, which evaluate the contribution of each fracture to the flow. However, the influences of fracture intersections are ignored during the calculation. In this study, influences of fracture intersections on the permeability prediction are studied. The result shows that the predicted flow rate can only have a good accuracy when there is an infinite-length fracture with a larger aperture. Based on this conclusion, three inferences for the applicability of geometric predictive methods are proposed: (a) for fracture networks where all fractures have infinite length, the predicted permeability can have a good accuracy; (b) for fracture networks containing both infinite-length and finite-length fractures, the predicted permeability is only accurate when the infinite-length fracture have a larger aperture; and (c) for fracture networks where all the fractures have finite length, the error rates of predicted permeability increase as the aperture ratios of fracture sets increase. Sixty-three sets of discrete fracture network models are generated for verification, and these numerical results validated our proposed inferences.