Influence of confining stress on energy evolution of sandstone under triaxial compression

Through triaxial compression tests on sandstone at different confining pressures, the linear relationships between the peak stress and elastic modulus with confining stress were obtained. In order to obtain the energy of the sandstone with different axial strain, the relationship of strain energy and strain at different confining pressures were fitted by the stress-strain curve. The characteristics of energy evolution in the compression process are analyzed, which can explain the reason why the rock failure is even more intense with higher confining stress. The concept of crack propagation factor, T, was proposed. An empirical expression was derived to relate T and axial stress with different confining stresses. By doing this, we can obtain the actual rock mechanical parameters in different stages during the damage process of the sandstone by compression. Also, through the variation trend of T value, we illustrated why a plastic platform appeared near the peak intensity during high confining pressure. © 2014 EJGE.