On Establishing the Factors Determining the Choice of Methods, Schemes, and Systems for Mine Ventilation

A. F. KARATAEV

(Presented by the scientific conference of the Mining Operations Faculty).

General Remarks

The present work sets itself the task of generalizing and establishing the factors that determine the choice of methods, schemes, and systems for mine ventilation.

The consideration of these factors is carried out with regard to the mining and geological conditions of the Kuzbass.

The coal deposits of the Kuzbass are represented by series of seams containing a large number of thick seams with steep and inclined dips. Individual seams within the series are sometimes closely spaced. All coals of the thick seams, and some of medium thickness as well, are prone to spontaneous combustion. Almost all coal seams are also gas-bearing and dangerous with respect to dust.

These specific properties of the Kuzbass deposits require, for the correct determination of the field of application of the principal methods, schemes, and systems of mine ventilation, a detailed investigation of the factors determining their choice. This proposition is also confirmed by the practice of mining operations in Kuzbass mines. Thus, for example, at the Ordzhonikidze mine of the Kuibyshevugol Trust, with the designed central ventilation scheme, the working faces in the locked part of the mine field proved to be heavily gassed. This constantly led to stoppages of mining operations. Replacing the central mine ventilation scheme with a flank scheme would have provided the working faces with a sufficient quantity of air. If the mine shafts and the main crosscut had been laid near the locked part of the mine field, then even with the central mine ventilation scheme the working faces would have received a sufficient quantity of air, because the air paths would have been shorter. The use of a forcing-and-exhausting method would likewise have supplied the faces with air even under the central mine ventilation scheme. With this method of ventilation, the fans would have provided the required depression necessary for moving the calculated quantity of air. Under the adopted method of opening the mine field, the central ventilation scheme, and retreat extraction of the level—rather than advancing extraction, as is practiced at the mine—the faces, even with the existing fan installation, would have received the required quantity of air, because the main and ventilation drifts would have been under conditions in which their cross-sectional dimensions would have been preserved.

This example shows that in mines with nonuniform gas emission from the seams, gas abundance is the decisive factor in choosing the method and scheme of mine ventilation, the location of the mine shafts supplying air, and the direction of coal extraction in the level.

The mining of coal seams that are gas-bearing, prone to spontaneous combustion, and hazardous with respect to dust leads to an even greater interrelation between the method of opening and preparing the mine field, the mining systems, and the method, scheme, and system of mine ventilation. This interrelation increases with the growth of mine output and the depth of mining operations. Consequently, the identification and generalization of the factors determining the choice of rational methods, schemes, and systems of mine ventilation is highly important.

Requirements Imposed on Rational Methods, Schemes, and Systems of Mine Ventilation

In a country of victorious socialism and building communism, the methods, schemes, and systems of mine ventilation that are used must above all ensure the safety, reliability, and economy of ventilation. These requirements are achieved by:

1. Strict observance of the requirements of safety regulations with respect to the methods and schemes of mine ventilation.

2. The use of branching of ventilation currents, which is of particular importance in the mining of gas-bearing coal seams and seams prone to spontaneous combustion. This principle ensures safety and economy.

3. Stable operation of fans working in parallel.

4. Ensuring minimum coal losses in safety and protective pillars.

5. Minimum capital and operating costs.

The data set forth above make it possible to conclude that the principal indicators of the rationality of applying mine ventilation methods, schemes, and systems, from the standpoint of ventilation, are:

1) the magnitude of the overall mine depression, or the maximum depression required to move the calculated quantity of air through the mine;

2) the magnitude of air losses;

3) the magnitude of coal losses in shaft pillars and in pillars above haulage drifts;

4) the amounts of capital and operating costs.

Factors Determining the Choice of Mine Ventilation Methods

If the mining of noncombustible and non-gas-bearing minerals permits the use of any ventilation methods, then the mining of gas-bearing coal seams requires the exhaust method of ventilation, while coals prone to spontaneous combustion require the forcing method of ventilation.

As the depth of mining increases, the minerals and the rocks enclosing them change their properties, which determine the possible method of ventilation at the depth being mined. Thus, for example, hard coals when mining the first level are in most cases non-gas-bearing, which makes it possible to use any ventilation method if the coals are not prone to spontaneous combustion. The mining of subsequent levels is associated with an increase in gas content, which leads to the transfer of non-gas mines into the category of gaseous mines, for which only the exhaust method of ventilation is permissible.

Coals prone to spontaneous combustion require such a method of ventilation in which air losses to the surface, through the worked-out space and pillars, would be the smallest. Air losses depend not only on the magnitude of the depression determined by the adopted ventilation scheme, but also on the order in which mining operations are conducted, i.e., direct or retreat mining, the mining system, the depth of mining, the thickness of seams,

properties of the rocks of the floor and roof, the angle of dip, etc. Therefore, the correct choice of the method of ventilating a mine extracting a mineral liable to spontaneous combustion is possible only with a comprehensive consideration of:

1) the properties of the mineral: gas content, susceptibility to spontaneous combustion, dustiness, and the explosibility of the dust;

2) the conditions of occurrence of the mineral: depth of occurrence, thickness of the deposit, angle of dip, properties of the roof and floor, etc.;

3) the mine ventilation scheme, the location of the mine shafts supplying air, and the direction of coal extraction within the level;

4) the system of mining and the method of controlling the enclosing rocks;

5) in the case of explosive mine dust, the direction of the haulage flow.

It follows from the foregoing that the possibility of applying one or another method of ventilation depends above all on the properties of the mineral being mined and on the conditions of its occurrence, which in turn determine the method of developing the given deposit.

Factors Determining the Choice of Ventilation Schemes for Mines and Stoping Sections

The properties of the mineral determine the methods of ventilating mines and stoping sections, which in turn establish the location of the fans and the method of connecting them to the ventilation network, as well as the order of air movement through the mine workings, i.e., to some extent, the ventilation scheme.

The conditions of occurrence of the mineral, together with its properties and the properties of the enclosing rocks, determine the rational method of opening up the mine field, the order of working a level (advance or retreat mining), and the mining system (chiefly the method of roof control). The adopted method of opening up the mine field establishes the location of the intake and return shafts, which determine the mine ventilation scheme, while the adopted order of working a level and the mining system determine the ventilation scheme for the stoping sections.

Consequently, the principal factors determining rational ventilation schemes for mines and stoping sections are the properties of the mineral and the conditions of its occurrence.

It follows from the above that the choice of rational ventilation schemes for mines and stoping sections from the standpoint of ventilation is possible only with a comprehensive consideration of the following questions:

1) the opening up and preparation of the mine field for extraction;

2) the order of working the sections;

3) the choice of mining system;

4) the ventilation regime of the mine, as conditioned by the adopted organization of mining operations.

By the ventilation regime of mines and stoping sections one should understand:

1) the magnitude, the character of distribution through the mine workings, and the constancy of the depression necessary for moving the calculated quantity of air through the mine and the stoping section;

2) the magnitude, character of distribution, and constancy of air losses caused by the adopted organization of mining operations;

3) the degree of influence of natural draft on the ventilation of mines and stoping sections.

The basis for choosing rational ventilation schemes for mines and stoping sections, as is evident from the foregoing, must be a comprehensive consideration of ventilation and the conduct of mining operations.

Factors Determining the Choice of Mine Ventilation Systems

An analysis of the ventilation of large coal mines of the Kuzbass shows:

1. The size of the ventilation section along the dip is determined by the air-carrying capacity of the cross sections of the shafts and main crosscuts that supply air to the mine, depending on the daily output and gas abundance of the mines.

2. The size of the ventilation section along the strike depends on the location of the shaft supplying air to the mine, the number of wings in the mine field, and the mine ventilation scheme, and is determined by the magnitude of the maximum permissible total mine depression \[2, 41\].

The foregoing makes it possible to formulate that the principal factors determining the mine ventilation system are:

1) the air-carrying capacity of the standard cross sections of the main crosscuts and mine shafts;

2) the maximum permissible depression required to move the calculated quantity of air through the mine;

3) the maximum capacity and maximum depression developed by modern fans;

4) the specific nature of the geological conditions of occurrence of the mineral deposit, determining the location of the opening and development workings.

Conclusions

The choice of rational methods, schemes, and systems of ventilation is an extremely important and at the same time complex and difficult task, because the correct solution of this question depends on the physicochemical and petrographic properties of the coal and its enclosing rocks, and on a number of geological, mining-engineering, and economic factors.

All the numerous factors affecting the choice of rational methods, schemes, and systems of ventilation may be combined into the following two main groups:

Mining-geological factors:

Properties of the mineral deposit.

Geological conditions of occurrence.

Mining-engineering conditions of conducting mining operations, i.e., the method of opening and preparing the mine field, the mining system, and the ventilation regime determined by the adopted order of conducting mining operations.

Economic factors:

1. The cost of driving and maintaining ventilation workings.

2. The cost of electric power for operating fan installations.

3. The cost of ventilation equipment.

4. Wage costs for servicing ventilation.

5. Costs associated with losses of the mineral deposit in protective pillars.

Consequently, for the correct choice of the system, method, and scheme of mine ventilation, all the factors indicated above must be considered comprehensively.

LITERATURE

1. Skochinsky A. A., Komarov V. B. Mine Ventilation. Ugletekhizdat, 1951.

2. Karataev A. F. On the question of applying district (sectional) ventilation in coal mines of the Kuznetsk Basin. Izvestiya TGII, vol. 67, 1949.

3. Skochinsky A. A. A Brief Synopsis of a Cycle of Lectures on Explosions of Gas (Methane) and Dust in Coal Mines. Gosstekhizdat, 1940.