Permeability variation around underground openings is of great importance to many engineering concerns, especially for the geological disposal of radioactive waste. The permeability of ground is changed by excavation due to blasting and stress redistribution. Hence, the modeling of rock joint behavior should consider not only dilation, closure, shear and joint propagation, but also changes in the flow permeability and retardation capabilities. To determine the stress-flow relationship of the rock joint, one needs to calculate the flow rate through the joint under different mechanical stresses.
In this study, it has been pointed out that the percolated discontinuity is very sensitive to the normal stress. Under a low normal stress, the shear strain may allow asperities to climb on top of each other for the two adjacent rock surfaces, thus opening up the fracture aperture. On the other hand, under a high normal stress or for relatively soft materials, the shear force may deform and damage the asperities, and the aperture characteristics will be drastically changed.
Permeability around underground openings will be changed by the stress redistribution caused by excavation. Different physical models may lead to quite different results. Besides, for different joint roughness, spacing, and depth, the extent to which the permeability is changed may be different. There is a possibility that for deep openings in a good quality rock mass, a decreased permeability is more likely to be induced by excavation, while for shallow ones in a heavily jointed rock mass, an increased permeability will be caused and the JRC has much more influence on the behavior.
