Vol 38 Iss. 1

Topics of research work of the Department of Mine Ventilation and Safety Engineering of the Leningrad Mining Institute are aimed at ensuring normal ventilation of mines, creating safety conditions in mine workings and such sanitary and hygienic working conditions that would make it possible to achieve maximum productivity.

In mine shafts, unlike other mine workings, the ventilation resistance of which is caused by the roughness of the walls, the resistance is created not only by the shaft walls, but also by the reinforcement located directly in the free cross-section of the air flow moving along the shaft.

The flow rate of mine main ventilation fans is spent on ventilation of all stoping and development faces ∑Qz; on short circuits arising between the fan channel and the outside atmosphere – external leakages; on countless short circuits arising in underground workings through leakages in ventilation structures, coal pillars and mined-out space – internal leakages, as well as on ventilation of machine and other chambers that need separate ventilation.

When developing medium thickness seams with gentle and horizontal bedding the panel system of development is often used. In order to speed up the construction period and quickly put the mine into operation, the deposit is opened by central twin shafts. The mine ventilation scheme at this method of opening method will be central.

The main harmful component of exhaust gases is acrolein (CH₂=CH‑CHO) - a colorless liquid with a characteristic sharp smell of burnt fats. Being in exhaust gases in the form of vapors, acrolein strongly irritates the mucous membranes of the nose, mouth and eyes. Its permissible concentration is 0.002 mg/l (0.00008% by volume). The content of acrolein in exhaust gases depends on the working conditions of the engine and its mechanical condition and, according to our measurements, ranges from 0.00330 to 0.0312%.

Air leaks in mines have been the subject of numerous studies in recent years. However, not all their types have been sufficiently studied yet. For example, air losses through pillars and stoppings separating parallel workings, through which the incoming and outgoing air streams pass, have not yet been studied.

The present work aims to establish the normal values of air leakage through the mined‑out space on the basis of mine observations carried out by the Department of Mine Ventilation of LMI during 1953 and 1954 at 75 mines in Donbass. Although observations of air leakage in 65 faces were carried out, the obtained material was still insufficient to establish the dependence of the norm of air leakage through the mined‑out space on the depression between the haulage and ventilation drifts, the seam occurrence, the nature of the roof rocks, the depth of mining, the face advance rate, etc. All these factors have a greater or lesser degree of influence on air leakage through the mined‑out space. It is currently impossible to give an expression that would reflect the dependence of the air leakage value on all these factors. The solution of this complex problem requires additional research. We declined to solve this problem also for the following reason: as our observations have shown, when the specified factors change, they vary very insignificantly – within 5‑6%.

At coal and ore mines there are large air leaks, sometimes reaching 70‑90% of the fan flow rate. They limit production, create unsatisfactory working atmospheric conditions, contribute to the accumulation of explosive and harmful gases, and increase energy consumption for ventilation.

Internal air leakage of local ventilation fan at individual work. Local ventilation of dead-end mine workings during sinking is carried out by local ventilation fans and ventilation pipes. Mine pipelines are mostly leaky and leak a significant amount of air at the joints. The amount of air entering the face through the pipeline Qface can be so small that the ventilation will be ineffective even at fan capacity Qfan exceeding several times Qface. With the increase in the length of excavations, the control of air leakage along the length of the pipeline is of paramount importance.

In order to overcome the resistance of the air pipeline when air moves along it, it is necessary to create a pressure difference at its ends. As is known, in the absence of air leaks, depression ...

Determination of air dustiness during blast hole drilling on apatite‑nepheline rocks at the S. M. Kirov mine was conducted for a number of years by the mine's dust laboratory. It was found that some amount of dust remains in the air of the face even when drilling with water.

Currently, at a number of mines in the Stalin‑Makeevsk, Central and other areas of the Donetsk basin, the air temperature in the stoping faces (more than 30 faces) exceeds the limit (26°C) established by the Safety Rules, reaching 28‑30°C in the summer months. The most radical means of combating high temperatures, which at a certain depth of mining operations become inevitable, is artificial cooling of mine air. When choosing a cooling system, it is important not only to find a cheap and technically convenient way of obtaining cold, but also to correctly address the issue of the location and number of air coolers, so that air cooling is quite effective with the least expenditure of cold.

For a number of years, mainly in relation to the conditions of the Donetsk basin, studies have been conducted on mine thermodynamics, the development of measures to combat high temperatures in deep mines and the choice of rational mine air cooling systems .

Sudden emissions of coal and gas not only complicate the development of coal seams, reducing the rate of coal production and delaying the excavation of individual seams, but also are a great danger to the lives of workers. Foreign and domestic researchers put forward a number of hypotheses that differently explain this complex phenomenon of nature.

In the development of coal seams possessing high gas content, intensive gas emission is the most frequent and important obstacle in achieving high indicators of labor productivity. Particular difficulties arise in connection with the transition of mining operations to deep horizons and the development of thick coal seams even at shallow depths – about 200‑300 meters. The latter is characteristic for Kuzbass, where, according to G.D. Lidin, the methane content of preparatory works reaches 50‑60% of the total gas balance of mines. If we take into account that the level of methane content of mines in Kuzbass is less than in Donbass, it is easy to imagine the difficulties that will be encountered in mining operations in this basin in the near future. Some idea about the value of gas emission into the preparatory mine workings can be obtained from the data in the table. Already at a depth of 200‑300 m, it becomes extremely difficult to combat the increased gas emission by diluting methane to the established norm (not exceeding 1%).