## 3 Experimental Results and Analysis
### Cyclic Loading and Unloading Energy Evolution Law
At the same time, the difference in energy state drives the different deformation and damage modes of the rock. It can be seen that the ratio of elastic energy and dissipative energy-to-input energy affects the damage mode of the rock. Figure 7 shows when the loading rate is 0.5 \(\mathrm{KN/s}\). The variation of elastic energy ratio and dissipation energy ratio with axial stress of the rock. From the figure, it can be seen that the elastic energy ratio and dissipation energy ratio vary nonlinearly with the axial stress. The elastic energy ratio increases at the beginning of loading, and then increases when the loading reaches about 48% of the peak stress; it reaches the maximum when the axial stress is loaded to about 73% of the peak stress. The dissipation energy ratio exceeds the elastic energy ratio at the early stage of loading. This shows that the closed friction of microcracks and dislocation between rock blocks dissipate a lot of energy in the compaction stage, thus resulting in the proportion of dissipated energy greater than the proportion of elastic energy. As the loading continues, the dissipated energy ratio gradually decreases. From the initial loading to the loading of about 73% of the peak stress, the dissipation energy ratio decreases by about 30%. After that, the dissipative energy ratio increases. With the continuous expansion of microcracks, the specimens are continuously damaged, and the microcracks are connected from random and disorderly sprouting to orderly nucleation, thus forming macroscopic cracks and destabilizing extension. The ability of the rock to store elastic energy decreases, percentage of elastic energy decreases, and percentage of dissipated energy increases. This can be used as a precursor to destabilization damage in rock specimens. Figure 6: Rock energy evolution curve under different loading rates. It has been shown that rock energy evolution has a strong rate correlation [26; 27; 28; 29]. However, there is no uniform understanding of the variation of various forms of energy with the loading rate, so it is necessary to make an analysis of the loading rate effect of that. As Figures 8 and 9 represent, at different loading rates, the evolution law of elastic energy and dissipative energy with axial stress is similar, which has been analyzed in the previous section. The elastic energy increases with the increase of the loading rate. The increase of elastic energy with stress at the beginning of loading is not obvious. With the increase of axial stress, the loading rate effect of elastic energy is gradually amplified. Dissipation energy also increases with the increase of loading rate. This is because the increase of loading rate will lead to the increase of peak stress; that is, the rock strength will increase, so the input energy will also increase, and the energy allocated to elastic energy and dissipation energy will be increased accordingly. The distribution ratio of elastic energy and dissipated energy under different loading rates is shown in Figures 10 and 11. In different deformation stages, the percentage of elastic energy decreases with the increase of loading rate; the percentage of dissipated energy increases with the increase of loading rate. The more energy that is dissipated during the deformation of the rock, the more microcracks will be produced and fracture surfaces will be formed; at the same time, more fragments appear, and the fragment sizes become smaller. This explains the phenomenon that, the larger the loading rate, the more fracture surfaces, more fragments, and smaller the scale after damage. Figure 8: Elastic energy density change curve. Figure 7: Energy distribution ratio. Figure 11: Dissipation energy proportion curve. Figure 10: Elastic energy. Figure 9: Dissipation energy density change curve.