Fracture systems caused by mechanical indentation in medium or hard rocks

Fracture systems in brittle rocks induced by indentation are presented. These are based on numerous experimental results. Two models have been developed to account for the experimental observations and elucidate the failure mechanisms induced during indentation. One model concerns the indentation depth and the other describes the length of radial/median cracks remaining in the rock. Equations deduced from both models correlate well with experimental results in the laboratory. Modification of the equations makes it possible to take the fracture systems in the deep underground into consideration. The equations can serve for general use in many medium or hard rocks with different dimensions of indenters.