Reduction of ore losses on the footwall by improving ore breaking

Abstract

When mining steep deposits of Kryvyi Rih iron ore basin (Ukraine), a significant part of the reserves is lost in the “triangle” of the footwall. Complete extraction of reserves requires increased costs for mining ore. At present, there are options for mining reserves from the “triangle” of the footwall. However, all the proposed options lead to an increase in the cost of mining or increased ore losses and the reduced iron content in the mined ore mass. To reduce the cost of mining, an option is proposed with concentrated charges to break ore located between the footwall and the caved massif. In order to improve indicators of reserve extraction from the “triangle” of the footwall in the massif, it is advisable to place inclined concentrated charges at an angle of 58 – 78 degrees. To reduce broken ore dilution with waste rocks on the boundary, it is advisable to create an overcompacted layer of the broken ore mass by reducing the calculated value of the line of least resistance by a factor of 0.5 – 0.75. Application of this method of mining reserves from the block increases the content of iron in the mined ore mass by 1.2%, reduces discounted costs for driving workings and for drilling and blasting. Thus, due to application of the bulk level caving system with improved ore breaking by the use of concentrated charges located in the “triangle” of the footwall, the expected economic effect of mining of 718.2 kt makes 5.20 k USD.