Effect of rock-coal strength ratio on acoustic emission and fracture fractal characteristics of assemblage
In order to study the progressive failure characteristics of coal-rock assemblages in layered medium under the conditions of different rock-coal strength ratios,uniaxial compression experiments were carried out on coal-rock assemblages with different rock-coal strength ratios by using DYD-10 e-lectronic universal testing machine and PCI-8 acoustic emission signal acquisition system,combined with the theory of energy dissipation and fractal theory.The experimental results show that:the failure mode of the assemblage specimens with different rock-coal strength ratios is the shear failure of the coal body pulling the rock to form a fissure,which induces the rupture of the rock;the increase of the rock-coal strength ratio leads to a limited increase in the compressive strength of the coal-rock assemblage,and the coal seam is the main factor influencing the compressive strength of the specimen.The slopes of the fractal dimension Dc are all greater than those of Dr,indicating that the fractures are more complete-ly developed in the coal body during the full stress-strain of the coal-rock assemblage.When the rock-to-coal strength ratio increases,the energy storage limit of the coal-rock assemblage gradually decrea-ses,and the energy stored inside the specimen is not enough to drive the fracture to expand further into the rock layer.It is of great significance for the further improvement of the dynamics of coal-rock as-semblages in mining for the purpose of disaster prevention and control.
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