Numerical determination of deformability and strength of 3D fractured rock mass

Abstract

We used a systematic numerical method to determine deformability and strength parameters of a fractured rock mass with irregular and stochastic fracture systems in 3D. In this case, different DFN realizations were generated based on Monte Carlo simulation and then compliance tensors and Representative Elementary Volumes (REV) for rock mass deformability and strength were determined in 3D. Stress-dependent strength of fractured rock mass was examined and different theoretical and empirical failure criteria were adopted. The numerical modeling results show anisotropy in deformability parameters in different directions. The obtained rock mass deformability moduli and peak strength of rock mass are reduced expectedly compared to intact rock. The results were compared to the analysis in 2D which had been performed in the previous stages of this research work. The approximated REV of rock mass deformability and strength properties in three-dimensions were found to be smaller than those in 2D numerical simulations. The results of rock mass behavior under different sets of confinement stresses indicate that characteristic parameters are completely stress-path-dependent. The approximated characteristic parameters from Empirical Hoek & Brown (EHB) criterion shows that rock engineering design based on EHB generally is more conservative. The Mogi-Coulomb criterion, considering the intermediate principal stress, estimates different values of cohesion and friction angle of rock mass compared to the conventional and extensional tri-axial tests. Therefore, care should be taken when such parameters are used in rock engineering projects.