Progressive Failure Energy Index of Deep Marble under Different Stress Paths

In order to investigate the progressive damage characteristics of deeply buried marble under different excavation disturbances, RFPA^3D is used to carry out the progressive damage tests under three different stress paths of conventional triaxial loading, constant axial pressure unloading of perimeter pressure, and axial pressure unloading of perimeter pressure. A gradual damage stage division method is put forward based on the energy index, and the corresponding characteristics of the stress threshold is analyzed, and the characteristic energy change rule is worked out. Finally, the optimization of rock burst index R_e and brittleness index B_e is discussed in order to provide certain theoretical support for the investigation and design of deep underground engineering and underground energy exploitation. The study result shows that: As for different stress paths under the deep marble peak strength, peak strain is different. However, with the surrounding pressure, the unloading stress level increases. The elastic strain energy gradually decreases from the initial linear growth to the growth rate until it finally stabilizes, while the dissipated energy changes from slow growth to linear rapid growth .With the introduction of elastic energy growth rate k_e, the dissipation energy growth rate k_d can reasonably and accurately define the four stages of progressive damage of deep marble. Under different stress paths, the characteristic stresses have obvious enclosure effect. Under the same enclosure, the unloading characteristic stresses are smaller than the conventional triaxial loading. The corresponding characteristic energies increase with the enclosure and the unloading stress level, and the sensitivities of the elastic and dissipation energies to the stress paths are different. The rock burst tendency index R_e and brittleness index B_e are positively correlated, and the possibility of rock burst decreases with the increase of confining pressure and unloading stress level. This study can provide reference for related research.