ABSTRACT
A probabilistic model has been developed which, once the geometry of the discontinuities present in the rock mass is characterized, can be used to predict keyblock occurrence for proposed excavation geometries. Deterministic keyblock analyses determine what shapes of keyblocks are possible for a given excavation geometry and a group of specified joint orientations. The maximum removable area provides an upper bound prediction of the largest keyblocks which will be found, assuming that the rock mass contains only joints having the specified orientations. In order to simulate joint geometry, it is necessary to probabilistically characterize the jointing geometry present in the rock mass. A probabilistic model has been developed to take into account all of these critical parameters in order to give improved predictions of the expected frequency and size of keyblock occurrences.
