Research on loading rate effect of uniaxial compressive strength of coal

In order to investigate how the loading rate affects the uniaxial compressive strength of coal, the mechanical properties testing of 4-1 coal from Zhengli coal mine in Shanxi province has been carried out with the TAW-2000 electro-hydraulic servo rock mechanical experimental system. The correlation between peak strength, elastic modulus, axial strain and loading rate has been studied, and how the release and dissipation of elastic strain energy react with loading rate has also been discussed. The results of the study are as follows: 1) Unlike the brittle rocks, the peak strength of the coal samples will increase as the loading speed grows, but there is a critical value when the rate exceeds, the strength will decrease. 2) The damaging stress of the coal samples has negative correlation with the loading rate. 3) The quicker the loading rate becomes, the faster the axial stress grows. But when it exceeds 1.16×10-3 mm/s, the increment of the load would be stable. And the faster the rate is, the earlier damaging stress could be observed, and also the faster the samples could be damaged. 4) Conversion rate of the strain energy dissipation is relatively low in the first phase of the uniaxial compression tests, and has a negative correlation with the loading rate. In the second phase, the dissipation strain energy first increases and then decreases as the loading rate increases. The maximum conversion rate of strain energy dissipation occurs at the peak point or the point where axial the stress falls abruptly after the peak point on stress-strain curve. © 2016, Editorial Board of Journal of Mining & Safety Engineering. All right reserved.