Experimental research on influence of loading rate and confining pressure on energy evolution of coal

A serial of uniaxial and triaxial compression tests on coal samples under different loading rates and confining pressures are conducted by using the TAW-2000 electro-hydraulic servo system. The characteristics of energy dissipation of coal under different loading rates and confining pressures are studied, and the dissipation strain energy conversion rate is also discussed. The results show that the elastic strain energy increases at first and then decreases at stage I of the uniaxial compression tests, and the dissipation strain energy conversion rate, which has a negative correlation with the loading rate, is relatively low. At stage II, the dissipation strain energy increases at first and then decreases with the increasing loading rate. The maximum strain energy dissipation conversion rate occurrs at the peak point or axial stress suddenly falling point after the peak point of stress-strain curve. The dissipation strain energy conversion rate is very sensitive to the confining pressure. That is, the larger the confining pressure, the greater the dissipation strain energy conversion rate, and the faster the damage of the coal.