Study on mechanical properties and deformation of coal specimens under different confining pressure and strain rate

Abstract

In order to research the influence of confining pressure and strain rate on the mechanical properties and deformation of coal. The triaxial compression experiments of coal specimens under different strain rate and confining pressure were conducted. In this research, the strength, deformation behavior and failure mode, etc. of coal specimens were evaluated by experiment. The experimental results show that the strain rate mainly impacts peak and post-peak stages of stress-strain curves. The peak strain increases and then levels off with the confining pressure increase at low strain rate. The peak strain increases with the increase of confining pressure at high strain rate, but the increasing rate tends to be reduced. Peak strength, cohesion and internal friction are positively correlated with strain rate, respectively. And there is significant linear correlation between peak strength and confining pressure. For numerical result, macroscopic cracks appear firstly in pre-peak stage under uniaxial compression and firstly appear in peak stage under triaxial compression. Many fine tensile macroscopic cracks appear with the increase of loading at low strain rate and a wide tensile crack and few fine cracks appear with the increase of loading at high strain rate. The numerical results are consistent with change law of AE signals, AE signals are mainly in the pre-peak stage under uniaxial compression and AE signals are mainly in the peak stage under triaxial compression. The AE signal of coal specimens under low strain rate is more active than that of coal specimens under high strain rate.