Destressing technology for rock around coal mine roadways and its applications

Rock control methods around coal mine roadways can be divided into support and reinforcement methods and destressing methods,and the destressing is an effective way for rock control around the roadways with high in-situ stress and intensive mining induced stress. At present,the destressing technical system for rocks around roadways has been formed,which includes roadway layout,rock destressing in near field and in far field. The classification,mechanism,affecting factors and applicable conditions of various roadway destressing methods are introduced in this paper. The essence of roadway layout is to arrange the roadways in stress decreasing areas,such as under or over gob,along the edge of gob,or in gob,which is the first choice and effective destressing method. The rock destressing around roadways in near field mainly contains slotting,drilling,blasting and driving destressing roadways,and its destressing mechanism is to form some deformation space in shallow rock surrounding roadways,reduce rock displacement toward roadways,and transfer the high stress in shallow rock to deep rock. The rock destressing in far field mainly includes blasting with deep boreholes and hydraulic fracturing,which reduces the coal mining activity affect to roadway stability by means of cutting or worsening roof layers above roadways. In recent years,hydraulic fracturing has been widely applied,and become an effective approach for hard rock worsening above coal face and rock destressing around roadways subjected to intensive mining induced stress. In case study,the applications of regional and local hydraulic fracturing technology are introduced,including geological and production conditions,hydraulic fracturing design and destressing effects. Finally,the existing issues associated with roadway destressing methods are analyzed,the technical development prospects in future are put forward.