Determination of safe spans of mine workings based on the bearing capacity of rocks in deposit development

The article focuses on improving methods for calculating parameters of mining operations by accounting the strength of the rocks and the magnitude of natural and man-made stresses. The relevance of research in this area is determined by the fact that overstating the reliability of calculations increases non-recovered reserves, while understating increases the operating hazards. The correctness of determining the stability of the rock outcrop parameters increases when using the phenomenon of self-blocking of rocks upon their exposure. The permissible parameters of the stopes are determined based on generalization of the existing concepts, including the one by M.M. Protodiakonov, according to which only the mass of the rocks contained within the dome acts on the mine working. Information is provided on the state of the mining industry in Russia. The results of studying the stability of the ore-bearing rock masses are presented with the detailed description of the possibility to preserve the span of a flat roof during the development of narrow slightly dipping ore bodies. The paper defines the relationship between the span of the workings of infinite length, the height of the dome of natural equilibrium above it and the engineering and geological properties of rocks. An example of an engineering–geological study of an ore-containing rock mass with graphical interpretation is given. An algorithm has been developed for determining the safe parameters to control the state of the rock mass. It is proved that horizontal stresses play an important role in formation of stresses within the mined area, and controlling the state of the rock mass consists in utilizing the residual bearing capacity of rocks by limiting the length of the spans. It is concluded that the determination of the size of mine workings based on combined criteria of the rock strength and the stress values makes it possible to increase the safety of workers and reduce the dilution of ores with the gangue rock. The results of the research may be demanded in the underground mining of solid minerals.