Effect of loading rates and stress paths on rock strengths: a novel approach based on experimental evidence

Tests of rock strength under different loading rates and stress paths often lead to ambiguous results, as both factors are inter-playing each other. As a result, there is surprisingly little research into the study of unifying both factors when comparing the rock strengths from various triaxial compression tests. In this technical note, we propose a simple but rigorous mathematics expression to assess and compare the rock strengths under different loading rates and stress paths. To make the proposed method as accessible as possible to a broad application, we have derived the explicit forms of solutions for three popular rock failure criteria. We then examine and validate the proposed method using the results of triaxial tests on marbles and sandstones, based on the important Mohr-Coulomb criterion.