EFFECT OF FRACTURE ORIENTATION DISTRIBUTION ON BLOCK HYDRAULIC CONDUCTIVITY OF 2-D DISCRETE FRACTURE NETWORK SYSTEM

A program code was developed to calculate block hydraulic conductivity of the 2-D DFN(discrete fracture network) system based on equivalent pipe network, and implemented to examine the effect of fracture orientation distribution on the hydraulic characteristics of fractured rock masses through numerical experiments. A rock block of size 32 x 32 m was used to generate the DFN systems using two fracture sets with fixed input parameters of fracture frequency and gamma distributed fracture size, and various normal distributed fracture orientation. DFN blocks of size 20 x 20 m were selected from center of the 32 x 32 m blocks to avoid boundary effect. Twelve fluid flow directions were chosen every 30° starting at 0°. The directional block conductivity including the theoretical block conductivity, principal conductivity tensor and average block conductivity were estimated for generated 180 2-D DFN blocks. The effect of variability of fracture orientation block hydraulic parameters was found to significant for the DFN having low intersection angle between two fracture sets. The chance for the equivalent continuum behavior of the 2-D DFN system were found to decrease with the decrease of mean intersection angle of the two fracture sets.