Numerical study of fracture openings by tunnelling in fractured rock mass

We investigate the evolution of fracture opening in a discontinuous rock mass by considering the effects of decompression around a cavity using the 2D distinct element method, UDEC software, based on stochastic realisations of a fracture network model. A series of numerical experiments were conducted under realistic loading conditions to calculate voids between blocks supposed to represent mechanical apertures of fractures. Special emphasis is given to the influence of separation and rotation of blocks. These numerical experiments show that the distribution of mechanical opening values computed this way is much more heterogeneous than anticipated from the distribution of stress-correlated values of apertures from an a priori constitutive relation.