Experiment on the energy damage development process of water-saturated limestone under varied loading rates

Karst water damage is one of the more visible forms of subsurface engineering karst geological hazards. To investigate the energy damage evolution mechanism of saturated limestone under mining disturbance, uniaxial compression tests of dry and saturated limestone at various loading rates were performed in the rock mechanics test system, and the acoustic emission counts and energy evolution laws were thoroughly examined. The results show that the distribution trend of acoustic emission counts is independent of the loading rate; that the influence of water on the distribution trend of acoustic emission counts is primarily reflected in the development stage of unstable rupture; and that the maximum count rate of dry limestone is produced at the peak intensity, while that of water-saturated limestone is produced near the yield strength. The maximum elastic energy stored inside the rock before damage increases as the loading rate increases, the fraction of wasted energy to total input energy reduces, and the final strain of the rock before damage lowers. Water-saturated limestone have a lower ability to store elastic strain energy than dry limestone, and the percentage of dissipated strain energy declines quicker with strain, but at the critical point of instability damage, the percentage of dissipated strain energy is larger than in dry rock samples. Furthermore, by incorporating the energy evolution law of the rock loading process, a rock damage estimation technique based on energy dissipation was constructed, and the method's feasibility was demonstrated.