Study On Key Technology Of Blasting On Rock Bench Of Goaf Of Wujiata Surface Coal Mine

Rock bench blasting of goaf is a kind of more free surfaces blasting. As there are hole bottom free faces of roch bench, special requirements have been put forward for key parameters of blasting bench height, blasting hole net parameters, unit consumption of explosive, blasting methods and so on. It need not only guarantee personnels and equipments security on rock bench, but also ensure the blasting effect, which makes the key technology of the rock bench blasting to be particularly important.The coal mining method and goaf characteristics of small coal mines of Wujiata surface coal mine are analyzed systematically, the suspected goaf regional is delineated by using geological radar geophysical detection method, engineering detection method by drilling is put forward to determine the spacial characteristics of the goaf span, goaf height and so on. The control precision of goaf is improved by using triangle hole net to decrease the control range of the hole net. After analyzed the influence degree of goaf height to the operation equipments and personnels security on the overlying rock, the new concept on" goaf critical height "is proposed, the critical height of 12m stripping bench of Wujiata surface coal mine is also determined. Through analyzed and compared more calculation methods of safety thickness of overlying rock, a calculation method of the safety thickness of overlying rock of goaf is determined, which fully considered influence factors of explosive properties, rock properties, blasting hole net parameters. A new concept on safety bench height of overlying rock is proposed, the meaning of safety bench is cleaned. By using the model of goaf span and safety thickness of overlying rock built, safety bench height of overlying rock under different spans of Wujiata surface coal mine is determined, blasting bench hight ia also determined based on the safety bench height. The blasting model of overlying rock bench of goaf is built by using LS-DYNA software, blasting parameters of overlying rock bench of goaf are optimized. Two kinds of blasting scheme are proposed, one is adjacent benches drilled and blasted when the above berm width is not less than the minimum working berm width, the other is adjacent benches drilled and blasted when the following bench near to the above. Many groups of blasting industrial tests are carried out according to the results of blasting parameters optimized, the blasting technology of adjacent benches drilled and blasted when the above berm width is not less than the minimum working berm width, hole bottom back stowing and middle initiation is determined, which has been verified in rock bench blasting of goaf of Wujiata surface coal mine.