FAILURE OF THICK-WALLED HOLLOW CYLINDERS OF ISOTROPIC ROCK

A series of experiments were performed on thick-walled hollow cylinders of five different types of isotropic rock. The magnitude of the intermediate principal stress appears to have a marked and regular effect on the strength of these rocks. None of the commonly used failure criteria for brittle materials adequately describe the results of these experiments. A recent proposal to generate a failure surface for a given material by rotating triaxial test data about the σ1 = σ2 = σ3 principal stress axis seems to be supported by these test results at least at low confining pressures. There appears to be a smooth transition between extension and compression failure under combined polyaxial stress conditions. The possible effects of stress gradients on rock strength and the types of fracture observed in these tests are discussed. © 1969.