A simple, convenient three-dimensional Hoek-Brown criterion for rocks

Referencing the expression of the Ottsosen strength criterion for concrete, a simple three-dimensional Hoek-Brown(HB) criterion is proposed to overcome the shortcomings of the HB criterion, where the influence of the intermediate principal stress on rock failure is not taken into account. The mathematical deduction of three different expressions of the proposed strength criterion is made. Besides, the convex and smoothness of the failure envelope surface is proved. A non-linear multiple regression technique is adopted to obtain the best fitting material parameters, and Poly-axial test data for eight different rocks was used to verify the proposed criterion. In addition, a comparison of determination of coefficient for three different expressions of the proposed strength criterion is made. Further, a comparison of the new criterion with three existing ones is also made. The new 3D HB criterion is easier, robust and convenient to set up elasto-plastic constitutive models in future. ©, 2015, Academia Sinica. All right reserved.