Abstract
To analyse the effect of loading rate on the energy evolution of rocks under cyclic loading and unloading, tests on saturated limestone were conducted at loading rates of 0.15, 0.2, and 0.3 mm/min, and the evolution characteristics of plastic, elastic, dissipation, and input energies were examined under different loading rates. The results indicated that the plastic strain in the entire test was directly proportional to the loading rate. In addition, strength, residual stress, plastic energy, and dissipation energy under residual resistance were inversely proportional to the loading rate. The plastic strain exhibited a decreasing–stabilising–increasing trend, and the smaller loading rate delayed the “increasing” trend. The increasing extent of each energy exhibited the following trend: input > elastic > plastic > dissipation energy. Furthermore, the first three types of energy exhibited a slow–fast–slow–fast increase trend. The dissipation energy exhibited a fast–steady–fast–slow–fast increase trend. Additionally, the elastic energy index exhibited a large increase–steady increase–decrease trend, which was proportional to the loading rate. The damping ratio exhibited a decrease–increase–decrease–increase–decrease trend which was proportional to the loading rate in the compaction stage and inversely proportional to the plastic stage.
Highlights
In the processes of driving, blasting, and mining in deep mining operations, the surrounding rock alternately exhibits the states of pressure increase and release
Kim et al [16] studied the effect of loading rate on energy absorption via a uniaxial loading test, and the results indicated that as the loading rate increases, the energy absorbed by the rock decreases
This indicates that the difference in the plastic strain under influence of the loading rate is mainly concentrated in the softening stage
Summary
In the processes of driving, blasting, and mining in deep mining operations, the surrounding rock alternately exhibits the states of pressure increase and release. Li Yangyang et al calculated several types of energies using the stress–strain curve of cyclic loading and unloading They observed that as the loading rate increases, the proportion of dissipation energy to total energy increases in the early stages of loading and unloading [18], and it decreases before reaching the peak strength. The advancing speed of the working face affects the process of stress transfer of the surrounding rock [21], which leads to a change in the law of energy accumulation, release, and dissipation in the surrounding rock. The evolution processes of plastic energy, elastic energy, input energy, and dissipation energy of the rock under different loading rates were analysed
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