Experimental study on degradation of mechanical properties of coal and rock and multi-parameter characteristics of acoustic emission signals

Abstract

In order to investigate the fracturing process of coal subjected to cyclic loading, the mechanical properties and the acoustic emission characteristics of coal samples were analyzed using MTS815 mechanical testing machine and acoustic emission instruments. The results show that under different stress levels, the elastic modulus of coal presents a rapid increase, then slow increase and finally sharp decrease trend. Poisson’s ratio and irreversible strain show a three-stage trend, namely, a first slow increase, subsequently gradual increase and finally a significant increase. Low, medium and high frequency characteristic signals accounted for 77.41%, 6.18% and 16.41%, respectively. Among them, low frequency and high amplitude energy signal is the main characteristic signal to induce macroscopic fracture of coal sample. Microtensile crack and shear crack accounted for 37.9% and 62.1%, respectively. Finally, the damage factors defined based on the load-unloading response ratio can better characterize the damage evolution process at different loading stages.

Keywords

• damage evolution
• load/unload response ratio (lurr)
• acoustic emission
• multi-parameter analysis
• micro fissure