: In this study we examine six different failure criteria by comparing them to published polyaxial test data ( s1 > s2 > s3) for five different rock types at a variety of stress states. We employed a grid search algorithm to find the best set of parameters that describe failure for each criterion and the associated misfits. We found that the Modified Wiebols Cook, and Modified Lade criteria achieve a good fit to most of the test data. This is especially true for rocks whose strengths have a strong dependence on the intermediate principal stress. However, for rocks in which the intermediate stress does not affect failure, the Mohr-Coulomb and Hoek & Brown criteria fit the test data equally well, or even better, than the more-complicated polyaxial criteria.
A number of different criteria have been proposed to describe brittle rock failure. We tested two conventional “triaxial ” criteria, (Mohr-Coulomb and Hoek and Brown) and four true triaxial, or polyaxial, criteria (Modified Wiebols and Cook, Modified Lade, Circumscribed Drucker Prager and Inscribed Drucker Prager). The five rock types investigated were amphibolite from the KTB site, Dunham dolomite, Solenhofen limestone, Shirahama sandstone and Yuubari shale. In this paper we present the results and analysis for the Dunham Dolomite and Shirahama Sandstone. The polyaxial data of Dunham dolomite was obtained from Mogi (1971), and the data for the Shirahama Sandstone was obtained from Takahashi & Koide (1989).