Abstract: Many problems, such as the difficulty of controlling top seam caving, the high dust concentration, the low top-coal recovery rate, may occur in the process of fully-mechanized top-coal caving in hard roof. To improve the cavability of the top-coal and control the spontaneous combustion, the presplitting blasting and controlling boreholes were arranged alternatively in the air-return roadway of coal face 111 in Tingnan coal mine, Changwu, Shaanxi, then the deep hole presplitting blasting combined with dynamic pressure water injection were carried out during the mining operation. Thus, the recovery rate of coal face was improved by 8.5%, the coal dust concentration decreased from 12.7 mg/m3 to 8.9 mg/m3. Meanwhile, through the injection of flame retardants in the controlling boreholes, the calorific value was decreased by 470 calorie per gram, the water content was increased by 2.56%, which effectively delayed the thermal process, improved the working environment, and ensured the safety mining of fully mechanized sublevel caving in the easy spontaneous combustion and high coal-dust coal seam.

Key words: deep hole presplitting controlled blasting, top-coal caving, degree of difficulty of coal caving, dynamic pressure water injection