Combined method of opencast and underground mining of valuable ore

Abstract

The efficiency of the combined opencast and underground mining of deposits directly depends on the overburden amount within the open pit boundaries. The amount of overburden to be removed, in its turn, is determined by the angles of the open pit slopes. At the same time, the influence of the open pit slope angle on the amount of the rock mass within the open-pit contours increases in an arithmetic progression with the mining depth. This fact confirms the direct relationship between the open pit slope angle and the efficiency of the mining operations from both an economic and ecological points of view. The article considers the technology for mining steeply inclined deposits of valuable ores by means of underground chambers mined out in advance with consolidating stowing to support unworked sides of an open pit called “well”. The chambers which can be not only vertical but also inclined at an angle of 60-80° serve to create an artificial fence (a ring concrete support). The work of the fence supporting the open pit side is markedly different from that of retaining walls of any type since the consolidating stowing mixture used to create the fence provides an ideal contact of the concrete wall with the enclosing rocks, thus making it impossible for an artificial fence to overturn. The proposed combined mining technology is expected to reduce considerably the number of the overburden operations, to minimize the damage caused by mining operations to the environment, and to increase the intensity of mine workings.