Estimating Rock Mass Deformation Modulus for Excavation Disturbed Zone Studies

Abstract

The full scale deformation modulus that needs to be used in numerical models of tunnels, caverns and geological disposal facilities (or related tunnel research sites) is of fundamental importance to the stresses, displacements and magnitude of the excavation disturbed zone or EDZ that is predicted. An alternative to direct measurement which has merit in scoping exercises and may be accurate enough for detailed design is outlined in the paper. The method is derived from rock mass characterisation methods and. was initially based on correlation between Q and RMR to give access to additional case records. Key parameters in the new method include the seismic P-wave velocity obtained from seismic refraction surveys, or from cross- hole seismic tomography, the Q-value, the depth of the site and the physical properties of the matrix as described by its uniaxial compression strength and porosity. The method has been checked at hard rock sites with sparse or frequent jointing, and in weaker, porous rocks which have no relevance to waste disposal but which provide a large range of conditions for verification.