Strength criterion for intact rock
Based on studies of the peak strength for soil by the authors, a simple strength criterion for intact rock is obtained in the general principal stress space. There are two material parameters in the equation. One is the uniaxial compression strength of the rock; the other describes the influence of stress level, and similar parameters are well studied in soil mechanics. It is seen that the proposed general strength criterion represents well the strength of various rocks and can provide a useful tool for geotechnical engineering practice.