Progressive mitigation method of rock bursts under complicated geological conditions

Jingxi Coalfield, which is called “China's Geological Encyclopedia”, has a complicated geological condition. As one its representative mines, Muchengjian Mine has witnessed nearly thirty rock bursts in the past decade. Considering geological structures, the in situ stress state, and the burst proneness of coal, one typical mining area in Muchengjian Mine is selected for analysis where nearly one-third of rock bursts occurred. This analysis lays the foundation for selecting mitigation strategies. Results indicate that the blasting disturbance plays an important role in the intensity and the scale of these rock bursts. Jingxi Coalfield has three types of rock burst mechanisms: I (high in situ stress rock burst), II (high mining-induced stress rock burst), and III (high in situ stress plus high mining-induced stress rock burst). Therefore, we follow two guidelines for rock burst control. One is to mitigate the high stress concentration, and the second is to control the disturbance stress. On the basis of these two guidelines, we designed a progressive mitigation method of rock bursts (PMMRB): first, the weak disturbance destress techniques (e.g., large-diameter drilling, water infusion) are applied to weaken the strength and the burst proneness of coal and to expand crack zones to reduce the stress concentration; and, second, the strong disturbance destress blasting is applied if the release of stress concentration is not sufficient. PMMRB is adopted in a similar mining area with a higher in situ stress, which indicates that PMMRB is applicable to the control of rock bursts and the reduction of rock burst intensity.