Oversize Yield in Underground Mine Development

Stoping, which is the initial link in the chain of the production processes of coal-face operation, significantly determines the performance of handling and mining-and-conveyor equipment, as well as losses and ore contamination. The size of the broken ore determines the cost of its mechanical crushing before lifting. Besides, the quality of breaking has a direct effect on the efficiency of ore enrichment. This influence manifests itself mainly in a significant increase in the cost of mechanical crushing and grinding of the ore, which are the most energy-consuming processes in ore dressing. The share of breaking in the direct financial costs of hard ore development, depending on the rock strength, reaches 20 – 35 %. Assuming that the main purpose of blasting operations in the mine is the destruction of the rock massif with creating the conditions for high-performance execution of the subsequent production processes of ore extraction, one should be careful about cost savings on breaking. The fact is that the proposed activities that reduce the cost of drilling and blasting may result in general deterioration of the quality of breaking. Therefore, the criterion of efficiency of any variant of blast hole drilling is to be an integrated indicator of the overall economic result of the entire production process chain, from coal-face operation to enrichment. Naturally, under certain conditions, when the effect of the results of stoping has local nature, the calculations can be made not for the entire production complex. This work analyzes the existing methods of calculating the parameters of blast hole drilling (BHD) in longhole stoping and considers the mining factors that affect the efficiency of stoping in similar geological conditions, namely, the oversize yield and the cost of coal-face operation. In practice, there are no methods for calculating the parameters of BHD that would be recognized as uniform and quite satisfying the needs of enterprises in all regions and types of mining. Depending on the local conditions, the home-developed methods proven by the practice are used, which are improved with experience. This work shows the experience in ore stoping at the Zapolyarny mine, and provides the results of industrial observations of the actual oversize yield.