Abstract

The effect of the intermediate principal stress on the intact rock strength has been studied by several authors, however its influence on the post-peak behavior has not been completely studied, and can be of main importance at depth, where the rock mass contains few discontinuities and is subjected to a three-dimensional stress field. Therefore, the extension of a simple proposal for modeling the complete stress-strain curves may be very useful in practice. In this research, the feasibility of modeling the peak and the post-peak behavior, including dilation, under generic polyaxial stress conditions is studied, considering laboratory datasets for several types of rocks. Based on the weakening-strengthening mobilization theory, it is demonstrated that the Kim-Lade's polyaxial strength criterion is more appropriate to recreate the post-peak behavior and it is concluded that the parameter mobilization theory is also valid for polyaxial stress conditions. The critical plastic strain (CPS) required to mobilize the strength parameters is equivalent to the one obtained from conventional triaxial tests with a proportional factor that accounts for the intermediate principal stress. Finally, this methodology is validated for different stress paths in the octahedral plane.