Types, monitoring and prevention technology system of roof disasters in mining face in China

For a long time, roof disasters have been the main problem in coal mine safety production, and the number of death and occurrence of roof accidents in coal mine always takes the top spot. In this paper the properties of roof, characteristics of ground pressure and cases of roof disasters were investigated. The results show that there are three main types of roof disasters in mining working face: rib spalling and roof caving, roof collapse and roof cutting and supports crushing. The characteristics and causes of all kinds of roof disasters were systematically researched: rib spalling and roof caving mostly occur in soft coal and rock mass, and unreasonable coal mining method and working face management also cause the disasters. The sudden collapse of large area roof is usually caused by the instantaneous collapse of large area suspended roof in hard roof. The large area roof cutting and supports crushing mainly occurs in the working face with shallow embedment and thin bedrock or the roof ruptured at the coal wall due to the large cumulative subsidence. For monitoring, prevention and control of roof disasters in China, the technical framework of roof disasters panoramic monitoring and early warning is established. In the technical framework, the micro-seismic monitoring system is employed to monitor roof movement in the far field, the mine pressure monitoring system is used to monitor the roof movement in the near field, and the 3D laser scanning technology is adopted to monitor coal wall space-time spalling. Through analysis of the monitoring data, the activity law of stope rock and support working situations are dynamically mastered. Then roof disasters monitoring and early warning are implemented. A comprehensive roof disaster prevention and control technology system for the whole working face mining is put forward. Before working face mining, the works such as reasonable coal mining methods, reasonable working face arrangement, scientific mining design parameters and optimized equipment selection should be performed. Those are core technologies for roof disaster prevention and control. In the mining process, the support should work well and the weakening roof technology should be added to realize the roof disaster prevention in the working face.