Blast casting is a high-efficiency technique applied in surface mines for overburden removal and results in stripping cost savings. According to ballistic theory and center-of-mass frame basic movement principles, key factors influencing blast casting effect were analyzed, which include bench height and mining panel width, inclined angle of blast holes, explosive unit consumption (EUC), delay-time interval, presplitting, and blast hole pattern parameters. An intelligent design software was developed for obtaining better breaking and casting effect, and the error rates predicted with actual result can be controlled with 10%. Blast casting technique was successfully applied in Heidaigou Surface Coal Mine (HSCM) with more than 34% of material casted into the inner dump. A ramp ditch was set within the middle inner dump for coal transportation. The procedure of stripping and excavating was implemented separately and alternately in the two sections around the middle ramp ditch. An unconstrained-nonlinear model was deduced for optimizing the shift distance of the middle ramp. The calculation results show that optimum shift distance of HSCM is 480 m, and the middle ditch should be shifted after 6 blast casting mining panels being stripped.
With the deepening of surface coal mine, the application of combined surface mining with underground mining is increased now. According to the influence analysis of underground mining on surface coal mine end-wall slope, the thin plate model of mined slope was proposed with distortion and stress distribution of the girder studied. Considering the practice of combined surface mining with underground mining, the modified method was put forward. Based on the roof breaking law of mined slope, the minimum width of protecting coal pillar was elicited. Subsequently this paper took the combined mining practice of Anjialing surface mine as example to study the subsidence law of roof and the influence of underground mining to surface mine slope. The research conclusion indicates that under the condition of combined mining the deformation and subsidence of overlying strata are obvious with a clear lag time, and the ceiling distortion evokes distortion of mined slope, which can be used as the theory sustainment to stabilization of mined slope under combined surface mining with underground mining.
When two adjacent surface mines are simultaneously mined in the same direction with a certain relationship of the time and space, the mining arrangement of the former mine will greatly affect the mining plan and economic benefit of subsequent surface mine. In this paper, the optimized mathematical model is established with the mining conditions and economic benefits taken into account. e minimum cost of objective function is analyzed in the condition of considering the different transportation distance with different dumping amount and secondary stripping amount. At the end of this paper a conclusion is drawn that the reasonable dumping level is determined as 1130 based on the annual planning project location and stripping amount, which will reduce the cost of production and smooth the coal mining. Moreover, it is verified by an example to be correct that the mathematical model can be used to solve similar problems of tracing mining or adjacent districts mined in surface mines.
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