Vol 30 Iss. 1

On January 4, 1954, Professor, Doctor of Technical Sciences V. D. Slesarev passed away. He devoted more than 35 years of his activity to the domestic mining industry and headed the Department of Development of Stratum Deposits at the Leningrad Mining Institute for 20 years. V. D. Slesarev was the first promoter of the introduction of longwall mining in the Moscow Basin. This method seemed impossible at that time, but is now considered the only appropriate one. V. D. Slesarev is the author of the first and original theoretically substantiated studies of the manifestation of rock pressure in the Moscow Basin. Based on his personal experience, V. D. Slesarev developed and scientifically substantiated such issues as the dependence of rock pressure on the shape of the cross-section of workings, the choice of their shape and methods of driving workings depending on specific conditions.

Improving the systems and methods for developing thick flat dipping seams is one of the most difficult and at the same time urgent tasks facing the coal mining industry at the present time. The most rational system for developing such seams is usually considered to be inclined layer mining with roof caving, which has become widespread in the industry. Engineering analysis shows that this system has a number of shortcomings. The issue of creating a rational system for developing thick flat dipping seams cannot be considered resolved. A rational system for developing thick flat dipping seams should provide for the exclusion of manually erected support in the working face, as well as the use of a large seam thickness. Among the possible solutions to this problem, the system for developing thick flat dipping seams with forced coal caving is particularly simple.

Shot drilling is a mechanical method of breaking rocks. Unlike other methods of core drilling, it is characterized by the fact that the material that breaks the rock - shot - is not attached to the crown, but is freely located on the bottom of the well and can be continuously replenished during the drilling process. With the simultaneous action of the rotary motion of the crown and some pressure transmitted by the crown to the bottom, the shot located in the well is set in motion, resulting in the deepening of the well. The force transmitted by the shot to the rock, in places of contact of the shot with the rock causes stresses, the value of which, in order to ensure the destruction of the rock, must be no less than its tensile strength. Under these stresses, violations of the integrity of the monolith in the contact zone with the shot appear, as a result of which the separation of rock particles occurs. In turn, the shot must have sufficiently high mechanical qualities. The minimum consumption of shot must ensure effective destruction of the rock. The efficiency of drilling is largely determined by the quality of the metal of the drill bit. A certain correspondence between the mechanical properties of the crown and the shot is necessary. There is still no single scientifically substantiated opinion on the nature of the work of shot in destroying rock.

The greatest difficulties in the coal industry are presented by the development of thick steeply dipping seams. Development of thick seams usually involves high labor costs, significant timber consumption and entails greater coal losses than when developing seams of average thickness. Cases of self-heating of coal and underground fires occur more often when developing thick seams. Therefore, significant material costs are incurred for carrying out preventive measures and extinguishing fires, which increases the cost of coal and often leads to very significant losses of minerals. A major achievement of Soviet mining technology is the shield system of Professor N. A. Chinakala. It has found wide application in the mines of Kuzbass. The decisive factor that determined the high degree of reliability of the shield of Professor N. A. Chinakala, the rapid and wide introduction of this shield in the mining industry, is the direction of its movement down the dip of the seam. The proposed work is an attempt to shed light on issues related to the improvement of the design of shields and the possibility of their use in the development steeply dipping, very powerful strata.

The problem of determining the strong dimensions of horizontal workings support elements constantly arises both during the operation of a deposit and during design. Its correct solution largely determines the safety, economy and uninterrupted operation. The variety of conditions in which a mine working passes does not allow determining the load on the support in the general case. Let us consider the issue of the roof pressure on the support of a horizontal working carried out in solid layered rocks, secured by a frame support with a straight top. A layered medium, each layer of which is a plate with sealed edges, is a repeatedly statically indeterminate system, and solving the problem of the pressure of this medium on the support by conventional methods was considered unrealizable for a long time. For the first time, a method for solving this problem was proposed by V.D. Slesarev in 1939 and called by him the sliding working method [9, 10]. Later, the sliding working method was applied by A.P. German [2], G.N. Kuznetsov [5] and others. The proposed work is devoted to the further development and specification of the processes under consideration. The description of the processes of deformation and destruction of roof rocks given below, of course, does not exhaust the issue and is to a certain extent schematic.

Determination of the main parameters of development systems is a very important and complex task, the solution of which largely determines the successful conduct of mining operations. Identification of the degree of influence of fracturing on rock stability is of great importance for the correct determination of the parameters of development systems. Since at present it is not possible to do this by calculation, then along with laboratory studies of samples it is necessary to organize special experimental work directly at the mines in order to establish a correction factor for the transition from the strength of samples to the strength of rocks in the massif. The results of laboratory studies of the physical and mechanical properties of rocks can serve as initial data for calculations to determine the parameters of the system, but subject to the establishment of a correction factor for the transition from the strength of the sample to the actual strength of the rock massif. The method for establishing the correction factor should be based on: a) a thorough study of the geological conditions of the deposit (site); b) data from laboratory studies of rock samples; c) the results of experimental work and mine practice; d) based on the proposed development system. The successful solution of the problem of determining the sizes of the elements of the system largely depends on the detail and accuracy of the geological exploration data on the deposit and especially on the knowledge of the structure and disturbance of the rocks of both the ore body and the surrounding rocks.

Ore drawing from the mined-out space in the presence of surrounding rocks is one of the most critical moments, on which quantitative and qualitative ore losses depend. Some decrease in the quality of the mined ore at the final moment of drawing does not reduce the advantages of systems with mass caving and mass drawing, since the progress of enrichment technology allows for a more confident use of mass mining methods with subsequent processing of minerals at enrichment plants. The results of ore drawing are determined not only by the appropriate organization and control during this process, but also by the correct choice of individual design elements - the "ore drawing horizon". These design elements include the distance between the discharge funnels, the slope angle of the funnel walls, the diameters of the lower and upper bases of the funnel, the difference in marks between the "release horizon" and the undercut horizon, etc. When drawing through funnels of the same height, but with different slope angles, the rdrawing figure will be maximum for the funnel with the optimal angle slope. The transverse dimensions of the discharge figures depend not only on the physical and mechanical properties of the flowing bulk materials (or ore), but also on the nature of the funnel surface. The greatest extraction of pure ore, a later onset and a slow increase in dilution are characteristic of discharge through funnels with an optimal slope angle. The height of the discharge funnel (with an optimal slope angle and a constant height of the ore layer) cannot be arbitrarily large, since this leads to an increase in the distance between the discharge openings, isolated discharge and an increase in ore losses in the ridges. Conclusions made from experiments on ore drawing from a single opening are confirmed by experiments on discharge from a number of adjacent openings. The optimal slope angle of the funnel should be the starting point in determining the distances between the discharge openings.