Research on surrounding rock failure law of large mining height working face in thick loose layer based on microseismic monitoring

The research on the movement law of surrounding rock under the condition of thick loose layer and thin bedrock mostly adopts theoretical research methods such as establishing a mechanical model and numerical calculation. It lacks research based on field dynamic measurement. The microseismic monitoring technology has been widely used in mine dynamic disaster monitoring and early warning in recent years. However, there are few studies on the failure law of surrounding rock under the condition of thick loose layer and thin bedrock based on microseismic monitoring technology. In view of the above problems, taking the 16001 working face of Zhaogu No. 1 Coal Mine of Coking Coal Energy Co., Ltd. as the engineering background, a high-precision microseismic monitoring system is established. The system is built by selecting the network arrangement mode of the borehole-roadway union. Based on the microseismic monitoring results, the dynamic failure law of surrounding rock in large mining height working face under the condition of thick loose layer and thin bedrock is studied. According to the accumulated released energy of surrounding rock, the energy density of the microseismic event is analyzed by adopting a nuclear density analysis method so as to achieve the purpose of studying the fracture development of the surrounding rock. The analysis results show that the maximum roof damage height is 87.8 m, and the maximum floor damage depth is 21.7 m. The maximum values all appear in the square stage of the working face, at which the roof water inrush risk is the highest. In the square stage, the roof-bearing rock beam is damaged, abnormal pressure occurs, and the damage degree of the roof, floor and advanced support is intensified. The results verify the existence of the stress breakdown effect. The sandy mudstone 48.3 m away from the roof of the working face is the key layer of the roof water barrier. The siltstone 67.7 m away from the roof is the breakdown control layer. The sandy mudstone 26.6 m away from the floor is the key layer of the floor water barrier. The results of microseismic monitoring and analysis are verified by bottom borehole peeping. The results show that the floor damage depth in the square area is more than 18 m, and the floor damage depth in other areas is 12-18 m. These results are consistent with the microseismic monitoring results.