Enhancement of the technology of caved ore drawing from the ore deposit footwall “triangle”

Abstract

Abstract In mining iron ore, over 60% of underground mines at Kryvyi Rih iron ore basin apply a system with the bulk caving of ore and overlying rocks. However, when the deposit dip is 45-60 degrees, application of this mining system leads to losses of about 30-40% of the footwall ore. Available methods of the loss reduction result in an increase in production costs or a decrease in the iron content in the mined ore mass. After analyzing the mechanism of forming the figure of drawing, it is proposed to change its parameters without significant costs due to the use of an inclined plane and an overcompacted ore layer. The presented study enables stating that with an increase in the inclined plane angle from 45 to 75 degrees the draw crater radius increases from 2 to 7.5 m, and a decrease in the factor of first loosening of ore leads to an increase in the radius of the crater to 10 m. Thus, for the first time it is proved that a decrease in the first loosening factor leads to the increased semi-minor axis of the ellipsoid of drawing and the width of the active drawing area, which will reduce losses of caved ore when drawing it from the stoping block in the footwall area. It is established that in order to minimize losses and dilution of ore when using level mining systems, the drawpoint should be located in the block sill at a distance ensuring formation of the 20 to 25 m high ellipsoid of drawing. In case of an overcompacted 22 m thick ore layer, it is possible to significantly reduce ore losses from 14 to 10% and ore dilution from 16 to 9%, thereby enhancing ore mass extraction indices without additional costs.