Theories and methods of efficiency water conservation mining in short-distance coal seams

The exploitation of underground coal resources can easily lead to the loss of precious shallow water re- sources,which leads to the death of surface vegetation and the imbalance of ecosystem. To protect the shallow water re- sources (river,lake and diving of quaternary sand aquifer),which maintains the ecological environment of the western mining area,especially to protect the underground diving ( ecological) water level,the concept of water conservation mining in short-distance coal seams was put forward based on the previous theoretical achievements of water conserva- tion mining in shallow single coal seam and the experience of rock control engineering. The concept integrated the protection of ecological water level,and the prevention and control of water inrush. In order to achieve an efficient water conservation mining under the mining conditions of short-distance coal seams and extremely short-distance shallow wa- ter resources,this paper studied the technical problems,such as the collaborative control of strata water-conducting fractures in the disturbed area of repeated mining,the low-damage control of ultra-thin barrier layers and the monito- ring and warning of water inrush (outburst) on mining surface. The study presented the long wall water conservation mining method,the water conservation mining under continuous mining and filling with wall system and the infrared monitoring and warning methods for water inrush in working face to realize the safe and efficient mining. More specific- ally,the methods included the strata control of short-distance coal seams,the calculation of the height of water-conduct fractures,the deformation calculation of aquicludes,the infrared radiation theories of loaded coal and rock,the control of water diversion fractures in the disturbed area of repeated mining,the filling body actively connected to the roof and the rapid operation technology among mining,supporting and transportation. Meanwhile,the weak areas of water con- servation mining were determined. Based on water resource protection,the optimized working face layout of shallow buried and short-distance coal seams,mining method allocation and water resource movement monitoring,an efficient mining theory was formed. The achievements have been achieved in the practice of water conservation mining in north Shaanxi and north China,which provides supports for green mining in China.