Different bedding loaded coal mechanics properties and acoustic emission

Abstract

Using TAW-2000KN electro-hydraulic servo rock press machines and the American Physical Acoustics Company’s SH-II acoustic emission systems, experimental studies began to address the mechanical properties in different beddings of loaded coal and the related acoustic emission characteristics, established based on the acoustic emission damage model, and verify the model. The results show that the mechanical properties of different coal sample beddings are distinctive, with maximum uniaxial compressive strength and elastic modulus of vertical stratification of coal samples and the minimum Poisson’s ratio. Thus, the minimum uniaxial compressive strength and elastic modulus of oblique bedding coal samples along with the maximum Poisson’s ratio in the processes of loading result in different bedding coal samples having different stress–strain curves, especially when different bedding coal samples experience the stages of fissure compression, elastic deformation, plastic deformation and instability and destruction. In addition, the displacement proportions of each stage of the loading process have relatively obvious differences: the loading times of vertical, parallel and oblique bedding coal are 495, 382 and 331 s, respectively, and their acoustic emission mutation points of peak stress are approximately 60, 41 and 33%, respectively. Thus, we can use the mutation point as precursor information to estimate the damage intensity in different bedding seams. The theoretical and experimental stress–strain curves obtained by the coal damage model are basically identical, verifying the reliability of the model and reflecting the feasibility of acoustic emission technology in the study of coal damage. The results can effectively forecast coal and gas outburst hazard in coal mines, especially highly gassy and outburst mines. It can also make comprehensive predictions for flooding accidents, roof fall accidents and other disasters, and provide valuable evacuation time for underground coal mine workers. The results are of great scientific significance in safeguarding the safety of coal mines.