Feasibility study on the influence of discontinuities on anisotropic rock masses regarding the stiffness

For the design of rock engineering projects, rock mass parameters are usually determined by the use of classification systems (Q, GSI, RMR, etc.). A homogeneous rock mass with reduced parameters via empirical relationships is generated, and the influence of the anisotropy is lost during the process. The influence of discrete discontinuities on the global rock mass stiffness is investigated in this feasibility study and the results compared to empirical solutions based on the GSI. The results show that with one joint set oriented perpendicular to the direction of loading, the block volume is rather insignificant for the resulting E _rm ; whereas the joint normal spacing parallel to the direction of loading and the block shape are the most influencing factors. In the cases, with the block volume and joint condition as input parameters, the E _rm is significantly underestimated, while the E _rm , based on RQD and JCond ₈₉ still fits in the range of the numerical results. However, the numerical investigations are so far limited on an orthogonal oriented joint network under uniaxial compression and further investigations are necessary.