On prevention and control mechanism of deep hole blasting in deep mining

Most of the coal mines in East China, Northeast China and North China have been mined below 600m depth, and dynamic disasters such as mine earthquakes have occurred frequently, which seriously restrict the safety, green and efficient production of coal mines. In view of the frequent occurrence of mine earthquakes under thick and hard roofs in deep coal mines in China, this study takes Dongtan coal mine as an example, and uses the methods of field monitoring, theoretical analysis and numerical simulation to elaborate the effect of deep-hole blasting roof pressure relief on the prevention and control of mine earthquakes, the pre-cracking mechanism and the influence on the overburden activities during mining process. It is found that the deep-hole blasting technology could effectively weaken the thick and hard overlying strata, release the strain energy accumulated in the overlying strata, and reduce the risk of large energy mine earthquakes. Based on the theoretical analysis of rock failure zone under explosion load, the rock fracture zone, fracture zone and effective failure range of deep-hole blasting are calculated. Combined with the monitoring of working face support, the deep-hole blasting technology could actively regulate the mine pressure and avoid the appearance of strong mine pressure. The numerical simulation model of the whole process of coal seam mining with four deep-hole blasting is established, and the evolution characteristics of stress and displacement of overburden before and after blasting are analyzed. In addition, the influence mechanism of deep-hole blasting on overburden activity during mining is revealed. The pressure relief technology of broken roof by deep-hole blasting could effectively weaken the thick and hard roof above the coal seam, reduce the compressive strength of thick and hard roof and increase the coefficient of crushing and swelling of overburden, which could be used to prevent and control the occurrence of strong mine earthquakes in deep mining.