2016 Volume 122 Issue 11 Pages 603-615
To investigate the effects of confining pressure and pore water pressure on the strain behavior and deformation properties of Aji granite, triaxial compression tests were performed at a constant strain rate (5.0×10－6 s－1) under confining and pore water pressures of 10-40 MPa and 10-30 MPa, respectively. During the tests, axial and radial strains were measured by two biaxial strain gauges. The results revealed increases in maximum differential stress and onset of dilatancy with effective confining pressure. Young's modulus tended to increase with confining pressure and decrease with pore water pressure. However, Poisson's ratio remained nearly constant under these experimental conditions. Dilatancy is related to the formation of micro-cracks during deformation and is enhanced at low confining pressures under dry conditions. In contrast, it tends to be suppressed at a high pore water pressure (low effective confining pressure) under wet conditions. These results indicate that stress concentration at the crack tip can be relaxed by the presence of pore water. Moreover, water injection into the specimen during wet experiments rapidly increases at a stress level of ~96% maximum differential stress. This rapid increase can be attributed to the formation of a micro-crack network.
