ABSTRACT
A rock mass containing a considerable number of discontinuities with low strength compared to the rock material is referred to as a blocky rock mass. The behaviour of a blocky rock mass is dominated by the properties of the discontinuity system. Despite its importance the determination of the discontinuity properties is subjected to several restrictions. In tunnelling the documentation of the faces is performed while construction work proceeds. Due to the pressure of time and the limited access only selected discontinuities are mapped in a manual sketch. Due to the lack of information detailed stability analyses of blocks are not possible to provide an objective basis for the final design of excavation and support. A new approach to overcome the described problems is currently under development. The approach includes the data acquisition process, the establishment of a geotechnical model, and the analysis of keyblocks. The stability analysis of keyblocks in a blocky rock mass is addressed and the important influencing factors such as the keyblock geometry are discussed. This method follows a hierarchical structure which allows for a consistent analysis
and objective auditing. An additional benefit of this computer-based method is gained from the high visualisation capability.
