Impact of fracture length distribution on seepage characteristics of fractured rock masses

Abstract

This study presents a numerical investigation on the effect of fracture length distribution on the equivalent permeability of fractured rock masses. Three-dimension discrete fracture network (DFN) models with different fracture length distributions were generated using Monte Carlo method. The equivalent permeability was calculated by simplifying the 3D DFN models to equivalent pipe network (EPN) models. The results show that the equivalent permeability becomes less scattered with increasing side length of sub-models (L n), showing a clear tendency of reaching a representative element volume (REV) size. The root mean square (RMS) = 0.2 is utilized as the threshold to determine the REV size. The REV size of the DFN model is approximately 4.17×104 m3 in which the power exponent (a) of fracture length distribution is 4.5. The fracture density (P 32) decreases exponentially with the increment of a. This is because the number of short fractures in the DFN model with a larger a is larger. The P 32 of the DFN model is positively correlated to the equivalent permeability.