The Failure Surface of Isotropic and Anisotropic Rocks under Multiaxial Stresses

A newly designed triaxial testing machine was used to investigate the ultimate strength of sandstone and crystalline schists under multiaxial stresses. Each specimen used was 5.5 cubic cm in size, and the capacity of the testing machine was 200 tons vertically and 100 tons in each horizontal axis. The experiments were carried out under stress-controlled condition (8tons/min). Rubber sheets with silicon grease were always used to minimize...