Despite the improvement in knowledge about rock mechanics and ground control, the mining of orebodies continues to present significant risks.
Depletion of mineral resources near the surface is in fact leading to mining at greater depth, which poses increased risk for the stability of excavations and, as a result, for workers. The use of technological tools to evaluate these risks must be followed by a comparison of the results with a failure criterion suitably representing the rock mass.

To evaluate the uniaxial compressive strength of a rock mass, the researchers proceeded with diamond drilling of distinct diameters on three sites of different depths at the CANMET laboratory mine in Val-d'Or. The results of their tests showed a reduction in the average strength and average deformation modulus based on sample size. Two approaches were then used to estimate the unit block strength, the first based on a statistical approach, and the second, on the rock large scale deformation modulus by means of in-situ dilatometer measurements. The report describes the evaluations of the strength of hard rocks resulting from each of these approaches.