EXPERIMENTAL STUDY ON ENERGY EVOLUTION OF SANDSTONE UNDER DIFFERENT STRESS PATHS

In order to study the energy evolution characteristics of rock, conducting uniaxial compression test, conventional triaxial compression tests and unloading triaxial compression tests of sandstone were performed by an MTS815 rock mechanics test system. The results show that:the increase of the dissipated energy is the performance of the internal damage and crack growth; in the elastic-plastic stage, the percentage of dissipated energy in proportion to total energy under conventional triaxial compression test is larger than that of unloading triaxial compression test and uniaxial compression test; the maximum limit storage energy increase linearly with confining pressure; under conventional triaxial compression test, the rock has the highest energy storage limit, the unloading triaxial compression test takes the second place and uniaxial compression test is the lowest. The increasing rate of dissipated energy before and after peak strength also have a good linear relationship with confining pressure; the rate after peak strength is much bigger than that before peak strength; it shows that the damage rate before peak strength is small, while damage develop rapidly after peak strength, and the suddenly steep increase of dissipated energy indicate the occurrence of rock failure.