Most of the existing models of the mechanisms of drilling and cutting processes are oversimplified in both stress state and failure criterion. On the other hand numerical modelling techniques are a more versatile method with great potential for development._x000D_
In reviewing drillability and predicting performance of excavation machines the empirical tests, which simulate the physical breakage action in excavating processes are seen to be the best in terms of penetration rate predictability. Future methods of determination of drillability should concern the breakage characteristics and rock abrasivity involved in the two basic types of attack, i.e., percussive and rotary drilling.