ABSTRACT
The true triaxial test of sandstone in the full stress space, with arbitrarily given I 1 and θ σ, was carried out by the improved control of stress loading and unloading methods. The test results show that the failure stress values can reflect the characteristics of unequal tensile and compressive strength of rock on the π plane. Compared with the two-dimensional generalized Hoek-Brown criterion and the three-dimensional Hoek−Brown criteria, the envelope shape of the generalized Zhang−Zhu criterion is the most consistent with the distribution of rock failure strength test data points, and has the highest fitting accuracy. The effect of increasing the Lode angle on rock failure properties is opposite to that of increasing the stress level. The test results reflect the nonlinear ductile-brittle transition law of the rock failure characteristics in three-dimensional stress space and π plane, which can provide guidance for the safety and stability analysis of deep underground engineering.
