Study on coal rib burst mechanism and its energy release characteristic in deep roadways

Rock burst disaster has become a major safety problem in underground coal mining worldwide. Using the true triaxial electro-hydraulic servo loading test system, the stress-strain law, failure characteristics and acoustic emission activity law of coal-rock combination, deep coal body and shallow coal body with three different stress types are studied. The strength criterion relationship of deep and shallow coal bodies is established, the energy release characteristics of deep coal body are analyzed, and the instability mechanism of deep coal body is revealed. The results show that the coal samples with different stress types are affected by the stress environment and structural differences. The shallow coal samples of the roadway rib and the coal-rock combination samples of the roadway rib under high σ₂ confining pressure all produce rapid stress drop after the peak stress, and the brittle failure and impact are strong. In the failure mechanism, the shallow coal sample of the roadway is mainly controlled by the tensile-shear coupling mechanism. The deep coal sample of the roadway is mainly controlled by the shear mechanism. The area near the constraint surface and the free surface of the coal-rock combination sample is controlled by the shear and tension-shear coupling mechanism respectively. Under the condition of same confining pressure, the shallow coal body of the roadway is more likely to be destroyed. Based on the source of the impact energy release of the roadway coal rib, the instability model of the coal body in the deep roadway is established, and the instability mechanism of the coal body in the deep roadway is revealed.