Investigation of rock pressure and strata convergence with a descending working horizon in extensive deposits at Krivoi Rog

Abstract

1. In the Krivoi Rog mines, disruption of workings on the draw and haulage horizons, caving of the roof, and deformation of the ore masses and rocks in the footwall occur owing to rock-pressure phenomena during the development of mass caving of the rocks in the hanging wall. 2. The rocks of the hanging wall are caved to the level of the working horizons; the caving pitch decreases with depth. 3. With two-stage working of the levels, thick pillars are not an effective way of combating rock pressure. They are deformed and their working is difficult, involving high losses and dilution of the ore. 4. For beds of considerable extent the most effective method is simultaneous, continuous single-stage mining of the ore on several horizons. The horizons should be worked from the center to the flanks, mining operations in the upper horizons being in advance of those in the lower ones. The over-all height of the horizons worked simultaneously should be greater than the height of the caving pitch. With this order of working the take, caving of the rocks in the hanging wall will display a lag; this ensures that mining-out takes place at stable exposures of the rock in the hanging wall.