Vol 46 Iss. 1

As is known, the gas balance of a preparatory working consists of two main components: gas emission from the face and from the sides of the working. Therefore, the study of the patterns of gas emission from the exposed surfaces of the seam into the preparatory working is of great practical importance both for organizing the ventilation of the working during its development, and for determining the influence of gas emission from preparatory workings on the gas content and gas balance of the section and the mine.

Working in a quarry is subject to the influence of meteorological conditions characteristic of the area and harmful impurities emitted into the atmosphere of the quarry during various production processes. Precipitation, changes in temperature and wind speed at the surface entail changes in the corresponding parameters at workplaces. The most unfavorable of all natural factors is temperature, since most of the quarries of the USSR are located in the zone of sharply continental climate with average winter temperatures of minus 15-20 ° and summer temperatures of +20-30°.

Methane emission within the extraction panel depends on the operation of mining machines, atmospheric pressure fluctuations, collapse of the main roof rocks, non‑uniformity of air supply, etc. Regardless of the influence of these factors, the methane content in the outgoing air stream of the panel should not exceed 1%. Consequently, it is necessary to supply to the panel such amount of air Qcalc that would ensure compliance with the requirements of the Safety Rules for any combinations of these factors.

During the operation of mines, there is a need for depression surveys and ventilation surveys, during which the following are measured: the total fan air quantity, the amount of air entering the mine, air leaks, the amount of air reaching the stoping and development faces, depression of individual air currents, sections and the mine as a whole, and other ventilation parameters. As a result of the survey, measures should be outlined to improve the ventilation of the mine, including reducing air leaks.

Calculation of mine air ducts by analytical and graphoanalytical methods is mainly reduced to the determination of two quantities: 1) air leakage or the delivery coefficient μ; 2) the head h, which must be provided so that a given amount of air Qzab reaches the end of the stack of pipes. Many formulas for calculating these values have been proposed. A. I. Shvyrkov, on the basis of theoretical studies of air movement in air‑permeable pipelines, established a functional dependence between these quantities.

The phenomenon of air recirculation during the operation of partial ventilation fans as a cause of gassing of dead-end excavations is insufficiently studied. As is known, recirculation at partial ventilation is a harmful phenomenon, and in gas mines dangerous, as it leads to an increase in methane concentration in the workings above the established standards. In workings where blasting operations are carried out, recirculation prolongs the time of face ventilation and can lead to an increase in the concentration of harmful gases. I. A. Babokin, analyzing the causes of methane accumulation before blasting over a ten-year period, came to the conclusion that in 8% of cases the accumulation was due to recirculation. The current Coal and Shale Mine Safety Regulations provide a number of restrictions that preclude the possibility of recirculation.

The possibility of using the wet method of dust suppression at the mines of the Norilsk Combine during excavation, loading and transportation of coal was established by thermometric measurements of air and host rocks along the course of the ventilation jet. The research was carried out by the staff of the Department of Mine Ventilation of the Leningrad Mining Institute in 1959-1960.

The main means of dust control besides ventilation is irrigation. Production studies at coal mines have shown that irrigation reduces the dustiness of the air at workplaces by 5-15 times. Application of this effective method of dust suppression at the mining enterprises of the Far North is complicated by severe climatic conditions in underground workings and low temperature of rocks. The air temperature in the majority of coal mine workings in the permafrost zone remains negative throughout the year, which excludes the use of water for dust suppression.

The study of the nature of gas distribution in the quarry at stable and unstable states of the atmosphere allows establishing the actual amount of air ventilating the quarry, taking into account certain atmospheric conditions. There is no information in the literature on the nature of gas distribution in quarries. V.S. Nikitin considers wind energy the main factor of natural ventilation of quarries. This is at variance with our experimental data.

Air exchange in quarries is formed under the action of wind energy and convective flows resulting from the temperature heterogeneity of the atmosphere by height. These factors can act together and separately . In the presence of wind and developed convective flows, air exchange is the most complete and active. The presence of only convective air flows in the absence of wind somewhat worsens air exchange, but provides active transfer of harmful impurities from the lower part of the quarry to the upper zone and beyond the quarry space. Sometimes wind energy is considered sufficient for air exchange in quarries. However, the decisive role in air exchange in quarries is played by convective flows, formed due to a certain temperature stratification of the atmosphere.

Local artificial ventilation of workplaces of quarries with the help of partial ventilation fans has not been studied so far, although in the literature there are indications of the possibility of its application in quarries. Experiments on ventilation of individual workplaces in Sibaysk and Mindyak quarries were conducted in November and December 1960.

The wide introduction of mechanisms with internal combustion engines in the mining industry has led to the need to create protective devices against harmful and poisonous impurities contained in the exhaust gases (carbon monoxide, nitrogen oxides, aldehydes, lead oxides, etc.). Depending on the type of engine and its design, as well as the fuel used, the composition of exhaust gases may vary.

About 40% of coal production in Kuzbass is accounted for by the Prokopyev‑Kiselevsky district. Of all commercial coal reserves as of January 1, 1960, 64.5% are concentrated in seams with thickness over 3.5 m, including 41.5% in seams with thickness over 6 m. Of the 25 mines in the district, seven are mining at the first, fourteen at the second, three at the third and one at the fourth horizons. Nine mines are preparing the underlying horizons, including four mines are preparing the second, four mines the third, and one mine the fourth horizons.

As is known, the main parameters of mines - productivity and service life - largely determine their technical appearance and the level of technical and economic performance. The choice of these parameters is related to the possible load on the seam, which for a single seam determines the production capacity of the mine, and for a suite of seams - also the sequence of their mining. Increasing the load on the seam and enlargement of mines are one of the main directions of technical progress in the coal industry in the coming years.