Study on safety of rockburst mine

Because of the lack of comprehensive evaluation on the control design reliability and their control ability of rockburst in current rockburst mines, the rockburst still occurs in some mines although the rockburst control measures have been taken. Based on the method of evaluating the safety degree by safety factor in geotechnical engineering, the basic idea of rockburst mine safety is put forward. Through site investigations, it is found that the damage area caused by rockburst is limited in proportion to the total working area of the working face. The stress concentration in the surrounding rock of mine roadway is limited, ranging from 1 to 6. The energy released by rockburst accidents is no more than 10⁹ J level, that is, the energy released by rockburst is limited. The safety evaluation of rockburst mine can be transformed into roadway safety evaluation, that is, the safety of roadway can ensure the safety of the whole mine. After rock burst occurs, controlling the shrinkage rate of roadway section within 20% can basically avoid casualties. Therefore, it is pointed out that rockburst can be prevented and controlled. Therefore, the conditions of non-occurrence of rockburst and occurrence of no casualties are put forward, that is, the actual load stress of roadway surrounding rock deformation system is lower than the critical stress of rockburst when roadway instability occurs and the energy released by the instability of the surrounding rock deformation system is lower than that absorbed by the surrounding rock support system. Safety evaluation should be carried out after impact risk evaluation, hazard classification and control design of rockburst, which includes critical condition, calculation of safety factor and classification of safety grade. Based on the instability theory of rockburst disturbance response, two aspects that need to be considered in safety evaluation are given: stress safety and energy safety. The stress safety is determined by the ratio of the actual stress under load to the critical stress of buckling in the surrounding rock deformation system (i.e. the stress safety factor). The energy safety is determined by the ratio of energy released from the instability of surrounding rock deformation system to the energy absorbed by surrounding rock supporting system (i.e. energy safety factor). Furthermore, the mine safety is divided into three levels: A, B and C, corresponding to safety, basic safety and unsafe respectively. Among them, if the stress safety factor is greater than 1.5 and the energy safety factor is greater than 1.0, it is a Grade A safe mine. The mine has control ability of rockburst and can be mined normally. If the stress safety factor is greater than 1.0 and the energy safety factor is greater than 1.5, it is a Grade B basic safety mine. The mine has control ability of rockburst and can be mined normally. If the safety factor is not Grade A or Grade B, it is classified as Grade C unsafe mine. The mine does not have control capability of rockburst or mining activities should be suspended. Taking a mine as an example, the complete flow of mine safety calculation and evaluation results are given. Finally, the stress safety factor and energy safety factor of some coal mines in China are given. Combined with the actual occurrence of rockburst in these mines, the reference of the calculation results of safety factor is verified, which shows that the safety evaluation method has certain reliability and practicability.