A simplified three-dimensional extension of Hoek-Brown strength criterion

The Hoek-Brown (HB) strength criterion has been applied widely in a large number of projects around the world. However, this criterion ignores the intermediate principal stress σ2. Many evidences have demonstrated that the rock strength is dependent on σ2. Thus it is necessary to extend the HB criterion into a three-dimensional (3D) form. In this study, the effect of σ2 on the strength of rocks is identified by reviewing the true triaxial tests...