EFFECTS OF FRACTURE TENSOR PARAMETERS ON DEFORMABILITY OF THE 3-D DISCRETE FRACTURE NETWORK SYSTEMS

The finite-sized fracture network system can affect the deformability of the fractured rock masses. This study addresses the effects of directional fracture tensor components and the first invariant of the fracture tensor on deformation modulus and shear modulus of the 3-D discrete fracture network (DFN) systems based on regression analysis performed between 3-D fracture tensor parameters and deformability of the DFN blocks. Using 1-2 deterministic fracture sets, a total of 224 3-D discrete fracture network cube blocks were generated with various configurations of deterministic fracture density and probabilistic fracture size distribution. The fracture tensor parameters were calculated for each generated DFN system. Also, deformability moduli with respect to three perpendicular directions of the DFN cube blocks were estimated using the distinct element method. The larger the first invariant of fracture tensor, the smaller the values for the deformability moduli of the DFN blocks. These deformability behaviors present an asymptotic pattern above a certain threshold. The threshold value should be evaluated differently depending on the configuration of fracture orientations and the mechanical properties of individual fractures. It is found that the power-law function describes the relationship between the directional deformability moduli and the corresponding fracture tensor components estimated in the same direction. The strong correlation between the directional deformability moduli of the DFN block and the corresponding fracture tensor component can be implemented to establish a constitutive model that describes the pre-failure behavior of the fractured rock masses.