Study on water-preserved mining technology of burnt rock aquifer beside the large reservoir in Shenfu mining area

Shenfu mining area is a China’s important coal production base and a typical high intensity mining field, and also a typical fragile ecological environment of arid and semi-arid areas,in which the burnt rock aquifer is one of the main groundwater resources. In order to study the influence and the protection of the burnt rock aquifer,taking the 5-2 coal mining in the first mining area of Zhangjiamao Mine field as an example,by studying the hydrogeological structure system and the water flowing fractured zone of 5-2 coal roof,this paper investigates the types and characteris- tics of water resources,establishes the water-preserved mining target of 5-2 coal seam,divides the water-preserved coal mining partition of 5-2 coal seam,and puts forward a new water-preserved coal mining technology which is burnt rock grouting curtain interception method. The results show that there are six main types of water resources in the study are- a,where only the burnt rock aquifer of 4-2 coal seam has the significance of water-preserved mining and the 5-2 coal mining area is divided into anhydrous mining area and water-preserved limited mining area of the 4-2 coal burnt rock aquifer. In the water-preserved limited mining area of 5-2 coal seam,the designed curtain wall spatial morphology,the position and quantity of curtain line and the row spacing and structure of grouting drilling are reasonable. In addition, the procedure and processes of drilling and grouting planed are scientific,and the implemented key technologies of grouting curtain,such as dual-site bidirectional water diversion grouting,zoning grouting of burnt rock full section,im- mediate test of anti-seepage and interception effect,are feasible. The pre-drainage of the 4-2 coal burnt rock aquifer of the working face before mining,and the measurement of the working face water inflow after mining in the water-pre- served limited mining area of 5-2 coal seam show that the static reserve and the dynamic recharge of the 4-2 coal burnt rock aquifer water quantity are about 20 000 m3 and less than 5 m3 per hour respectively. It means the grouting curtain closure realizes the effective isolation of the 4-2 coal burnt rock water inside and outside the curtain,and greatly re- duces the water discharge of the 4-2 coal-burnt rock water and the Changjiagou reservoir water with which it has direct hydraulic connection,and the protective mining effect of water resources is remarkable.