Research Of Mining Plan Optimization For Open Pit Coal Mines Considering Capital Investment

The optimization of mining schedule includes three elements:production capacity,mining sequence and mining life,while the existing mining schedule optimization is generally focused on obtaining the best mining sequence.There are two ways to deal with production capacity,the first is to determine a reasonable production capacity in advance based on the reserve size,which is used as a known condition in the mining plan optimization;the second is to establish a reasonable and limited range of production capacity,within which the mining sequence and production capacity can be optimized simultaneously.In the first case,the infrastructure investment is not a variable and does not need to be considered in the mining schedule optimization;in the second case,it also does not change much within the set production capacity range and is not considered as a variable in the optimization model,but in order to ensure the accuracy of the optimization results,the infrastructure investment is generally calculated based on the optimization results after the mining schedule is optimized and included in the net present value(NPV).However,infrastructure investment is a function of production capacity,while the three elements will interact with each other,with infrastructure investment not only affects the optimal production capacity but also,through the latter,the optimal mining sequence and mine life.Therefore,infrastructure investment must be regarded as one of the endogenous decision variables in the optimization of the mining schedule,and the three elements must be optimized as a whole to get the overall best mining schedule.To this end,this paper establishes a model and algorithm for mining schedule optimization by introducing the enumeration method to include the function of infrastructure investment as an endogenous variable in the optimization process.The basic models for the optimization of mining schedule in open pit coal mines include:a topographic model of the ground surface,a model of coal seams and final pit model.Firstly,a 3D topographic model of the ground surface is established by the altitute interpolation method under the condition that the ground surface contour line is known.Then,based on the drill hole data,selects the column model and use the inverse distance method to establish a column model of the coal seam.Afterwards,based on the topographic model of the ground surface and the column model of coal seams,the final pit is optimized by the cone elimination method.Secondly,based on the obtained final pit,the geologically optimum push-backs generation method is used to generate the geologically optimum push-backs sequence with the "maximum coal content".Then,the sequence of geologically optimum push-backs is dynamically sorted to form different subsequence paths from time 0 to the final push-back(the final pit).The NPV of the paths is used as the objective function,and the infrastructure investment function with the production capacity as the variable is incorporated as an intrinsic influence factor in the objective function,uses the enumeration method to construct an optimization model for the mining schedule of open pit coal mine,and the algorithm is established by the law that relying on old paths to construct new paths can reduce repeated calculations.After that,in order to solve the problem that the enumeration method is slow in optimizing mines with wide capacity intervals and many push-backs,the paper gives the mobile domain algorithm and its verification algorithm,the random fluctuation algorithm.Finally,the enumeration method of mining schedule optimization,which is improved by tthe mobile domain algorithm and the random fluctuation algorithm,is programmed into the CoalMiner software system and applied to a mine case.The results of the study show that the enumeration method considering infrastructure investment as an endogenous variable is more comprehensive,beneficial to risk avoidance,fast computing,it can optimize the three elements simultaneously,and its results are reasonable and practical.Furthermore,the resultsare are better than the previous mining schedule optimization methods without considering infrastructure investment as an endogenous variable in terms of production capacity,mining sequence,mining life,infrastructure investment amount,and net profit,which is an important reference for the design of the open pit coal mine.