Optimization of overcasting blast-dragline casting mining technology system’s parameters in fault subsidence zone of Heidaigou Open-pit Coal Mine

The fault subsidence zone of the coal seam in No． 2 mining district of Heidaigou Open-pit Coal Mine makes the overcasting blast-dragline overcasting mining technology system unable to be designed and constructed as the normal area,which affects the continuity of raw coal production. The influence range of the fault subsidence zone is deter- mined by analyzing the influence of faults on the stability of high bench of overcasting blast,the effective depth of in- clined perforation of drilling rig and the effective throwing rate of overcasting blast. According to the principle of the coal mining and casting working benches advancing rate equality,the functional relationship between the heights of overcasting blast bench,the thickness of raw coal and the production capacity of casting mining technology system is established,combining with the analysis of the production capacity of the dragline casting system,the curve equation of the relationship between the effective overcasting rate and the overcasting blast bench height,and the variation of the coal seam thickness,the overcasting blast bench height in the mining panel affected by the fault depression zone is pre- liminarily determined. On this basis,the top surface of the overcasting blast bench is adjusted according to the limita- tion of the longitudinal and transverse gradients of the drilling rig perforation,the overcasting blast bench height of each mining panel in the affected area of fault subsidence zone is determined. According to the fitting results of differ- ent overcasting blast bench blasting heap curves,analyzing the relationship between the height of the dragline standing bench and the production quantity of each part of the casting system,the functional relationship between the standing bench height of dragline and the production capacity of raw coal and the average thickness of raw coal is established. Based on that,according to the average thickness of coal seam in each mining panel and the casting amount of drag- line,the standing bench height of dragline in each mining panel in the affected area of fault subsidence zone is deter- mined. According to the variation of regional geological conditions in the fault-subsidence zone,the optimized parame- ters of overcasting blasting-dragline casting mining technology can guide Heidaigou Open-pit Coal Mine to realize safe and efficient production during the period of over-fault-subsidence zone and ensure the continuity of raw coal produc- tion.