Vol 58 Iss. 1

Outstanding scientist in the field of underground development of mineral deposits, Professor, Doctor of Technical Sciences, Head of the Department of Development of ore deposits of the Leningrad Mining Institute Vladimir N. Semevsky was born in 1898. After graduating from high school from 1918 to 1922, a Red Army fighter he defended the western borders of the young Soviet Republic.

Development of complex deposits of valuable multigrade ores is associated with the difficulty of not only selecting a system of development, but also to establish a relationship between the main parameters of systems and technical and economic indicators in different mining and geological conditions...

In the development of horizontal or declining ore deposits to improve the conditions of ventilation, prevent the penetration of water and gases, localization of cave-ins and other purposes it is sometimes necessary to leave barrier pillars that divide the ore body into separate fields. In case of significant ore reserves, these pillars are sometimes extracted after mining of adjacent fields...

The Kaula copper-nickel deposit was developed in the upper part by open pit and in the lower part by underground mining with priority extraction of chamber reserves. Recently, the second stage of development - excavation of the remaining ore pillars - has been switched to. The deposit is represented by a stratum-shaped deposit with variable thickness and dip angle; the depth of occurrence is up to 400 meters (vertically). The strength of the ore is characterized by a coefficient of 8-12, and of the host rocks - 8-14 according to M. M. Protodyakonov.

Development systems with open-cutting space provide intensive excavation, high labor productivity and relatively low cost of ore extraction. However, with such systems, ore losses steadily increase with mining depth. It is important to determine the economically permissible value of ore losses in the subsurface and, consequently, the maximum depth of development by open-pit systems. We consider the issue in relation to the conditions of the Kotselvaara copper-nickel deposit.

The Kirov mine of the Apatit Combine produces a stratum-shaped apatite-nepheline deposit with an average thickness of 150-200 m, located between the ijolite-urtites in the lying side and the ricechorrites in the hanging side. The extension of the deposit is northwestern, 310-320°, dipping at an angle of 30±5°. Protodyakonov strength: ore f=6-8, host rocks f=10-12. Horizontal and vertical excavations are often accompanied by a sudden separation (with a sharp crack) of pieces of rock from the contour and face of the excavation. This phenomenon, called shooting, is observed during excavation both on ore and on rocks of hanging and lying sides. The most active shooting is manifested immediately after blasting operations during the sinking of workings.

Based on the application of computer technology and methods of operational research proposed methodology for determining the rational parameters and design elements of cleaning blocks in underground mines Apatit Combine. The main provisions of the methods developed by Tsentrogiproshakht, IHD named after A. A. Skochinsky and Central Research Institute of Information and Technical and Economic Research of Ferrous Metallurgy were used.

In the practice of development of mineral deposits there are many cases of application of combined development systems with excavation of chamber reserves and leaving temporary pillars. In this case, at deposits with relatively stable ores and rocks, as a rule, the chambers are mined by highly efficient systems with subsequent filling of the excavated space with dry backfill material - rock from field workings and overburden of the open pit. In the left inter-chamber and inter-storey pillars often remains up to 50-60% of the total reserves of the deposit, which are extracted by labor-intensive and low-performance systems (layer caving, with the station bracing and backfill, etc.)...

Mining of ore deposits in conditions of increased mining pressure is often associated with dangerous stress concentrations that can cause harmful consequences for production: deformation of workings and separate sections of the ore body, crushing of pillars, self-collapse of ore and other phenomena that increase the danger of work, losses of minerals, labor and cost.

In recent years, in the development of valuable ores of non-ferrous and ferrous metals, development systems with concrete and solidifying backfill are becoming more and more widespread. These systems make it possible in some cases to conduct simultaneous mining of deposits by open-pit and underground methods, to preserve the surface from shearing and collapse, in other cases - to produce advanced excavation of rich ores, to extract the previously left pillars and to work fire-hazardous deposits with relatively small losses and dilution...

The ore deposit developed by the Mayak mine consists of disseminated and slump ores. Solid ores are located below the bulk of disseminated ores in highly fragmented and crushed rocks with sharply reduced stability. The thickness of these rocks in the immediate roof varies from 0.3-0.6 to 4.7 m, in the soil - from 0.5 to 5.5 m. The dip angle of the deposit varies within 3-12°, increasing up to 25-30° in some places on the flanks. The depth of development is 200-260 meters.

Blasting is still unavoidable in ore extraction, hence the process of mining is interrupted. Therefore, the maximum concentration of mining both in time and space, characteristic of modern mining, with the use of efficient mining systems and productive self-propelled equipment is especially important. The experience of domestic mining practice and conducted research, as well as the exchange of views at the V International Mining Congress held in Moscow in 1967 make it possible to outline some solutions in terms of directions for the development of technology of underground development of ore deposits.

Complexity of mining and geological conditions of occurrence and multigrade industrial grades of ores are characteristic features of many ore deposits. Development of such deposits often presents significant difficulties and requires a comprehensive technical and economic analysis to select not only the development system, but also the site or grade of ores of the first stage of mining. The optimum variant of development of deposits and the choice of the site of the first stage is determined by technical and economic calculation taking into account the planned indicators of production of a particular type of mineral raw materials, the peculiarities of mining and geological conditions, the number of ore reserves of each grade, the remoteness of deposits from the main industrial centers and the degree of economic development of the area of the deposit.

In connection with the transfer of the enterprise to a new system of planning and economic incentives, the cost of final products can no longer be the only criterion for economic evaluation of the enterprise. One of the main indicators of enterprise activity should be considered profit, determined by the expression...

In recent years, the mines have been using a system of development with solidifying stockpiling, which allows minimizing ore losses in the subsurface. At the Gaisky mine, where simultaneous development of the deposit by underground and open-pit methods is carried out, the effective, economically advantageous application of this system and safety of works in the open pit are determined by properly selected physical and mechanical properties of solidifying backfill...

The Khibinogorsk apatite-nepheline ore deposit developed by the Yukspor mine is a very thick (from 100 to 240 m) deposit with a dip angle of 25-45°. About 40% of the deposit's reserves are concentrated close to the day surface in hard-to-reach places on the slopes of the Yukspor Mountain.

In 1966 at the Kaula-Kotselvaara mine of the Pechanganickel Combine, experimental work was carried out on the development of an inter-chamber pillar located between the walls of the cement-reinforced backfill. Pilot works were carried out in a 6-8 m thick section of the ore body with a dip angle of 26-30°. The intervening rocks - phyllites - are partially broken by transverse fractures. In general, the ore and rock are stable. Ore strength coefficient is 8-12, rock strength coefficient is 10-12. Volume weight of the ore is 3.2 t/m³ and of the embedding material is 2.8 t/m³.

The existing methods of stripping in mass caving systems are usually characterized by a significant yield of large lump ore (over 250-350 mm). This is well illustrated by the example of Apatit mines. Table 1 shows the yield of lumps of various sizes depending on the method of stripping...

At the mines of Apatit Combine the labor productivity of workers engaged in ore output has increased due to the improvement of scraper delivery parameters; reduction of the maximum scraping length to 25-30 m, preparation of the block bottom with slick-less ore loading and application of scraper winches with a capacity of 75-100 KWt, as well as changing the ore condition for blocks with scraper delivery from 400 to 700 mm. This reduced oversize output and thereby increased net scraping time. The productivity of scraper delivery reached 300-350 tons/shift.

As it is known, the stability of pillars is significantly affected by the heterogeneity of rocks, presence of various layers, inclusions and ice. In order to clarify this influence in the Laboratory of Mining Pressure of LMI in 1963-1967 a set of studies was carried out, including the study of bearing capacity of pillars with weak interlayers of other rocks and ice inclusions for the conditions of Arkagalinskoye, Sangarskoye, Dzebariki-Khaya coal deposits and Baltic shale deposits...

Climatic conditions in the underground workings of highland mines in the Polar region have a significant impact on mining processes, as they lead to freezing of ore in ore chutes and outlets. One of the main causes of ore freezing should be considered the temperature and air regime of the mine. Cold air inflows along the path of the ventilation jet reduce its temperature. Cold air passing through wet beaten ore accelerates the heat transfer process. In addition, negative air temperature in underground workings serves as a source of colds of miners, causes freezing of air and water lines, is the cause of increased dustiness of the mine atmosphere.

A characteristic feature of deposits located in the permafrost zone is cementation of rock blocks with ice, which fills interlayer cracks and cracks that cut through rock layers, which promotes consolidation of layers and leads to an increase in the bearing capacity of the massif as a whole.

Of great importance in the choice of development systems with deep hole stripping is the mutual location of wells and fractures of the ore massif. This significantly affects the cost of 1 ton of extracted ore.According to VNIMI studies conducted at the Kaula mine field of Pechenganickel Combine, and according to the author's observations during the mining of four blocks of horizons 320 and 260 m of this mine, the fracturing of the ore body within the area under consideration is characterized by three systems of fractures: consonant, normal-section and oblique fractures in relation to the Main Tectonic Zone ...

Development of rock salt deposits by underground dissolution, as a rule, is carried out by cylindrical chambers arranged on a given (square or rhombic) grid. The calculation of parameters of stable chambers and separating pillars can be approached by the method of continuum mechanics, using, for example, the solutions obtained for vertical mine shafts. However, the continuum mechanics solutions are developed only for single excavations, and their application to the calculation of cylindrical chambers located on a given grid and having a mutual influence makes it necessary to introduce additional conditions.

Within the area of permafrost distribution there are large reserves of minerals, which are located in rocks with both negative and positive temperatures. Exploitation of deposits of this kind has very significant peculiarities in comparison with exploitation under normal conditions.

At present, the mining industry is increasingly using the method of contour blasting when sinking workings. Contouring of workings is carried out either before or after the destruction of the main mass of rock. According to this feature the main division of contour blasting is made: 1) preliminary slotting and 2) with subsequent contouring. The second method is used only for the purpose of ensuring the best conformity of the excavation cross-section to the design contour; the first, in addition, is more and more widely used in those cases when it is necessary to ensure the safety of some object beyond the design contour from the harmful effects of blasting.