New Criterion of Critical Mining Stress Index for Risk Evaluation of Roadway Rockburst

Risk evaluation of roadway rockburst refers to quantitatively dividing the rockburst-prone area into multiple sections with different risk levels at the mining design stage, according to the geological and mining technical factors influencing the rockburst occurrence, for partitioned and graded management of rockburst. Based on this, a targeted rockburst monitoring and early warning system can be formulated for mining working faces, and it is the premise of rockburst management and control. To determine the theoretical criteria of rockburst risk evaluation and improve the accuracy of the evaluation results, a mechanical analysis model of roadway rockburst with the structure of “elastic zone–plastic softening zone–fracture zone” was established. Theoretical calculation formulas for critical ground stress, critical mining stress, critical depth of the plastic softening zone, and fracture zone of rockburst occurrence were obtained. These were related to the mechanical parameters of the coal and rock mass, geometric parameters of the roadway, ground stress, and support strength. Accordingly, a critical mining stress index was defined (the ratio of actual mining stress to critical mining stress), a quantitative evaluation method for rockburst risk based on the critical mining stress index was proposed, and the process and steps of a critical mining stress index method for rockburst risk evaluation were explained. A rockburst risk evaluation was performed for the 302 (upper) working face in a coal mine in Shandong, China. The critical mining stress index method for rockburst risk evaluation was validated by comparing results with the monitoring data obtained using the drill cutting method, microseismic monitoring method, and comprehensive index evaluation method.