Experimental study on the influence of different bedding dip angles on mechanical properties of coal

In order to study the influence of bedding on the mechanical properties and permeability of coal samples, a triaxial gas seepage device and acoustic emission monitoring system developed by self-developed were used to conduct triaxial compression tests on coal samples at different bedding angles and to collect the corresponding acoustic emission data, and the failure forms of coal samples were analyzed combined with the Mohr-Coulomb strength criterion. The results show that the mechanical deformation characteristics of coal samples with different bedding angles have obvious bedding effects under triaxial loading, and the peak strength, elastic modulus and Poisson’s ratio all decrease first and then increase with the increase of bedding angles. The permeability of coal samples at each bedding angle shows the same trend, showing a U-shaped change of first decreasing and then increasing. At the same time, the initial permeability and minimum permeability of coal samples increase with the increase of bedding angle, and the C-90° bedding coal sample is 2.5-5 times that of other bedding coal samples. The acoustic emission signals are mainly concentrated in the yield stage and the post-peak failure stage, and in the post-peak failure stage, the ringing meter value of the coal sample reaches the peak. The acoustic emission signal generated by the coal sample at 0° is also the strongest, while the acoustic emission signal generated by the coal sample at 45° is the weakest. The Mohr-Coulomb strength criterion can well reflect the failure mode of coal sample with single stratified group, and the experimental results are basically in agreement with the theoretical analysis.