ABSTRACT
In order to investigate the failure mechanism of rocks under a three-dimensional compressive stress state, the Absolute Triaxial Testing (ATT) machine was developed, and the absolute triaxial tests were conducted by using a cubic specimen. Cubic specimens were chosen as the standard laboratory specimens. The test results demonstrate that no failure planes exist in the triaxial tests even though a large displacement occurs, while the specimen tested under a uniaxial compressive state fails due to separation rupture at the grain boundary. The stresses at failure of the specimen are shown in the Mohr's stress circles, which demonstrate that the Mohr-Coulomb failure criterion may hold for rock salt. In conventional triaxial tests, a cylindrical specimen is generally used to investigate the mechanical characteristics of geomaterials. Using the testing machine, simple shear tests were carried out in the laboratory on sand in an unsaturated condition, and its mechanical characteristics have been carefully investigated.
