Modelling excavation responses in jointed rock

Tunnel excavation in jointed rock causes complex changes in the surrounding rockmass that will generally result in increased permeability. New methods of describing the relevant rock joint behaviour, allow the physical and conducting joint apertures to be tracked in the course of complex tunnel-related loading histories, i.e. during joint closure, shear, dilation, shear reversal, cyclic normal loading, with asperity wear etc. This joint behaviour model has been incorporated as a sub-routine in the universal distinct element code (UDEC) for studying the changes in joint geometries that occur in the rock mass surrounding tunnel excavations, with and without internal or external fluid pressure. The graphical presentation of behaviour in the disturbed zone includes plots showing stresses and displacements, the magnitude and location of joint shearing, and the corresponding magnitudes of mechanical and conducting apertures of joints. A special tunneling problem in Oslo include analyses of joint conductivity changes caused by initial excavation, leakage control by subsequent systematic bolting, followed by final concrete lining with build-up of full external ground-water pressure