Classification of Methods, Layouts, and Systems of Mine Ventilation

A. F. Karataev

1. General Remarks

The grand tasks set before the mining industry by the decisions of the Nineteenth Congress of the CPSU require a fundamental improvement in the design of mine ventilation.

Mine ventilation is one of the most important factors determining the safe conduct of mining operations and increasing the labor productivity of miners.

A modern method for designing mine ventilation must be based on a thorough analysis of the factors that determine the rational ventilation of mine workings. This analysis is impossible without establishing a common understanding of the basic terms in mine ventilation.

In the technical literature on mine ventilation, there are still no clearly formulated concepts of what ventilation is, what a method of ventilation is, what a ventilation layout is, and what a ventilation system is. The absence of a unified understanding of these terms leads to their being interpreted in different ways, which makes it difficult to classify the methods, layouts, and systems of mine ventilation—a classification that is necessary for the rapid and correct determination of the conditions for the rationality of their application.

An example of different interpretations of the terms indicated above is the textbook on mine ventilation by A. S. Kovalev and L. D. Voronina, published in 1951. On page 127 it is written: “Such ventilation is called central”; on page 128: “These shortcomings are absent in another ventilation system—diagonal or flank. In this method of ventilation, the ventilation shafts are located on the boundary of the mine field”; and on page 129: “In view of these considerations, diagonal ventilation has up to the present time been used for shallow mines.” From what has been written above it follows that ventilation, a method of ventilation, a ventilation layout, and a ventilation system may all be central and diagonal. In reality, only the ventilation layouts of mines and extraction districts can be central and diagonal.

In S. A. Batalin’s book Ventilation in the Mines of Kuzbass, on page 13, it is written: “All the variety of ventilation layouts implemented in the basin can be reduced to the following five main groups:

1. Flank suction.
2. Flank combined.
3. Flank sectional.
4. Flank forcing.
5. Sectional combined” [2, 13].

Having established a unified understanding of the terms ventilation, method of ventilation, ventilation layout, and ventilation system, one can arrive at the conclusion that in the Kuzbass mines there are not five main groups of ventilation layouts, but one flank ventilation layout with various methods of ventilation;

in addition, from the point of view of ventilation, mines may constitute a single ventilation system or one consisting of several units that are independent in the ventilation sense, owing to the large dimensions of the mine [3, 498].

There is no single interpretation of the ventilation layout and ventilation system in D. Ya. Pravdenko’s book Ventilation and Lighting of Mines, Combating Fires, and Mine-Rescue Work, 1949 edition, page 193. Many more examples could be cited, but these are already sufficient to conclude that it is necessary to establish a unified terminology and classification of the methods, layouts, and systems of ventilation.

In the present work the following tasks are posed:

1) to clarify the terms: ventilation, method of ventilation, ventilation layout, and ventilation system, on the basis of the interpretation of the terms method, layout, system and of the materials set forth in the textbook by A. A. Skochinsky and V. B. Komarov, Mine Ventilation, 1951;

2) on the basis of a clear formulation of the concepts ventilation, method of ventilation, ventilation layout, and ventilation system, to classify the methods, layouts, and systems of ventilation.

2. Ventilation and classification of methods of mine ventilation

A characteristic feature of conducting underground mining operations is the need to supply all mine workings with a sufficient quantity of air of proper purity and temperature.

Atmospheric air filling the mine workings, over time, changes its chemical composition and physical properties. It becomes saturated with harmful, poisonous, explosive gases and mine dust; it changes its temperature, humidity, specific weight, and pressure. As a result of the indicated changes, atmospheric air filling the mine workings is transformed from pure air into vitiated air unfit for the normal functioning of the human organism, i.e., for normal well-being and working capacity. Therefore there arises the need to replace vitiated air with fresh (clean) air.

The process of removing vitiated air in general from any space and supplying clean air is called ventilation or airing [6, 6]. Consequently, by ventilation or airing of mine workings in mining it is necessary to understand the proper and continuous supply to them of a sufficient quantity of air of proper purity and temperature.

The movement of air through mine workings or mines is possible only when there is a greater absolute pressure at the entrance and a smaller one at the exit, i.e., air always moves from a space with higher pressure to a space with lower pressure. This is the fundamental law of the movement of air through mine workings [3, 219].

The difference of absolute pressures in the sections of mine workings, regardless of sign, in ventilation is called depression and is denoted by \(h\); it is expended in overcoming the resistance of the mine workings to the air moving through them.

Thus, depression \(h\), on the one hand, is the difference of absolute pressures in the initial and terminal sections of mine workings, and on the other hand, is the pressure expended in overcoming the resistance of mine workings to the air moving through them.

The Bernoulli equation for the movement of air through mine workings has the following form [3, 221]:

\[ h=(P_1-P_2)+(Z_1\gamma_1-Z_2\gamma_2)+\left(\frac{V_1^2}{2g}\gamma_1-\frac{V_2^2}{2g}\gamma_2\right), \tag{1} \]

where \(h\) is the pressure expended in overcoming all resistances to the movement of air through all workings along the path from the mine opening to the section in front of the fan.

In the right-hand side of equation (1) are represented those pressure differences which must be created or must exist in order for the given quantity of air to be able to pass through the mine.

Equation (1) shows that the pressure differences necessary for the movement of air through mine workings may be created:

1) artificially, by means of a fan, by creating a pressure difference \((P_1-P_2)\) in the initial and final sections of the air current;

2) naturally, by the pressure difference of air columns \((Z_1\gamma_1-Z_2\gamma_2)\), owing to the difference in specific weights caused by the difference in air temperatures at the surface and underground, and also by the movement of air at the surface (wind), which creates a pressure difference

\[ \left(\frac{V_1^2}{2g}\gamma_1-\frac{V_2^2}{2g}\gamma_2\right), \]

the case when air enters the mouth of an adit with velocity \(V\);

3) by a combination of the preceding methods.

Consequently, the ventilation of mine workings may be carried out by natural and artificial means and by a combination of the first two, i.e., ventilation may be natural, artificial, and combined.

In natural ventilation, the entry of air into a mine is effected, as indicated above, by the difference in air temperatures at the surface and underground, which leads to different specific weights of the air in the mine shafts supplying and discharging air. In addition, the entry of air into the mine may occur because of the presence of wind at the surface, while its distribution through the workings proceeds depending on the resistance of the workings to the air moving through them.

In artificial ventilation, the exchange of foul air for fresh air is carried out with the aid of fans, while its distribution through the workings may be effected depending on the resistance of the workings to the air moving through them, by artificially changing the resistance of the mine workings. The latter measure is used more often.

From the foregoing it follows that the aggregate of natural causes or artificial means of obtaining the depression necessary for moving air through mine workings should be called the method of ventilation or airing.

This formulation of the method of ventilation corresponds to the interpretation of the term method in general. In Russian, the term method is understood as one or another order, manner of action, or procedure in performing some work, in achieving some goal [5, 447].

According to Bernoulli’s equation (1), by the energy that creates the depression necessary for moving the calculated quantity of air through mine workings, all existing methods of airing or ventilation may be divided into two main groups (Fig. 1 and table):

Table

1. Natural methods of ventilation:
   a) those caused by the difference in air temperature at the surface and underground—“natural draft”;
   b) those caused by the presence of air movement (wind) at the surface.

2. Artificial methods of ventilation, with the aid of ventilators:
   a) forcing air into mines—the forcing method;

Fig. 1. Classification of methods of mine ventilation.
Legend:
rt—ventilation caused by a difference in temperatures,
v—ventilation caused by the presence of wind,
n—forcing method of ventilation,
v—exhaust method of ventilation,
nv—forсing-and-exhaust method of ventilation.

b) exhausting air from mines—the exhaust method;
c) simultaneously forcing air through one shaft of the mine and exhausting it through another—the forcing-and-exhaust method.

In view of the fact that mines always have natural draft, in addition to the two principal groups of ventilation methods there also exists a combined method of ventilation, i.e., ventilation is carried out simultaneously by natural and artificial means. Therefore, when designing mine ventilation it is always necessary to take into account the magnitude and direction of the natural draft.

In the operation of mineral deposits, in accordance with the PTE, it is required to have not fewer than two outlets to the surface in order to create a through ventilation current. The first outlet to the surface is the shaft of the hoisting mine, and the second is the shaft of the ventilation mine. In this case the movement of the ventilation current in stoping faces must be upward. Downward movement of ventilation currents in stoping faces is not permitted for the following reasons:

1. The use of natural draft in deep and in shallow mines during winter is made difficult, as is the removal of methane gas, which in stoping faces has an upward direction.

2. Gases from the worked-out space descend into the active workings.

1. Haulage of the mineral will be carried out through workings with vitiated air.

All the foregoing leads to a deterioration of atmospheric conditions in the mine both during operation of the fan and especially when it is stopped and then quickly started again. With a downward movement of the ventilation current in the working face, stopping the fan will cause reverse movement of vitiated air; quickly starting the fan again leads to reversal of the ventilation current, i.e., the vitiated air returns a second time into the working face.

Assuming that the shaft of the hoisting mine descends to the haulage level, and the shaft of the ventilation mine to the ventilation level (which often occurs in practice), with steep dip we obtain the following:

1. If the fan is installed on the surface and its discharge side (diffuser) is connected to the shaft of the hoisting or ventilation mine, then ventilation of the mine will be carried out by forcing air into the mine (Fig. 2).

Fig. 2. Forcing method of ventilation

In this case, installation of the fan at the hoisting mine provides an ascending movement of the ventilation current in the working faces, while installation at the shaft of the ventilation mine provides a descending movement of air in the working faces.

If the fan is installed on the surface and its suction side is connected to the shaft of the hoisting or ventilation mine, then ventilation will be carried out by suction of air into the mine (Fig. 3). In this case, installation of the fan at the shaft of the ventilation mine provides an ascending movement of the ventilation currents in the working faces, while installation of the fan at the shaft of the hoisting mine provides a descending movement of air in the working faces.

Fig. 3. Suction method of ventilation

1. When two fans are installed on the surface—one at the shaft of the hoisting mine and the other at the shaft of the ventilation mine—when one fan operates for forcing and the other for suction, the ventilation will be forcing-and-suction ventilation (Fig. 4).

Installation of the fan underground always leads to a forcing-and-suction method of ventilation. In gassy mines, underground installation is prohibited.

Since in stopes with an angle of dip \(\alpha > 5^\circ\) only an ascending movement of air is permitted, in the forced method of ventilation the fan must be installed at the shaft of the hoisting mine (Fig. 2a), and in the exhaust method of ventilation—at the shaft of the ventilation mine (Fig. 3b). This provision also applies to the forced-exhaust method of ventilation, i.e., the fan operating in forcing must be installed at the shaft of the hoisting mine, and the fan operating in exhaust—at the shaft of the ventilation mine.

Consequently, the adoption of one or another method of ventilation determines the locations of the fans and the manner in which they are connected to the ventilation network, as well as the order of air movement through the mine workings, i.e., to some degree the ventilation layout. Therefore, the design of mine ventilation should begin with the selection of the method of ventilation.

Fig. 4. Forced-exhaust method of ventilation

3. The concept of the ventilation layout of mines and mining sections

In the mining of minerals prone to spontaneous combustion, normal operation of mines is possible only when the ventilation layouts of mines and the ventilation layouts of mining sections are correctly selected. Although the field of application of ventilation layouts of mines and mining sections is determined by the same main factors, their interrelations in mines as a whole and in mining sections differ both among themselves and with additional factors; therefore there must be a classification of ventilation layouts of mines and mining sections.

By the ventilation layout of mines and mining sections one should understand a definite order of air movement through mine workings, which is determined by the arrangement of the mine workings, depending on the adopted organization of mining operations. This formulation of the ventilation layout corresponds in general to the term “layout.” In Russian, a “layout” is understood as a drawing depicting a system, the construction of something, or the interrelation of the parts of something [5,610].

The ventilation layout of a mine is determined mainly by the relative arrangement of the hoisting and ventilation shafts of the mine, while the ventilation layout of mining sections is determined by the location of the entry and exit points of the ventilation streams from the sections. These points, in turn, depend on the order in which development and stoping operations are carried out in the section.

4. Classification of ventilation layouts of mines and mining sections

On the basis of the concept of the ventilation layout of mines established above, depending on the location of mine shafts, two main…

new ventilation schemes for mines: central and flank (diagonal) (Fig. 5 and table).

In the central mine-ventilation scheme, the shaft that supplies air to the underground workings and the shaft that exhausts air from them are located in the center of the mine fields, if the mines are two-wing, or on one of the boundaries of the mine fields, if the mines are single-wing.

Fig. 5. Classification of ventilation schemes for mines and extraction districts.

Conventional designations:

ц—centrally offset arrangement of shafts,
ц.с—centrally paired arrangement of shafts,
ф—flank ventilation scheme,
к—wing ventilation scheme,
у—district ventilation scheme,
г—group ventilation scheme.

This scheme may have two variants of shaft arrangement:

1. “Centrally paired,” when both shafts, i.e., the hoisting shaft and the ventilation shaft, are located side by side in the center of the mine fields, if the mine fields are two-wing, or on one of the boundaries of the mine fields, when the mine fields are single-wing (Fig. 6).

Centrally paired arrangement of shafts.

Fig. 6. Central mine-ventilation scheme.

“Centrally offset,” when both shafts, i.e., the hoisting shaft and the ventilation shaft, are located in the center of the mine fields, if the mine fields are two-wing, or on one of the boundaries of the mine fields, when the mine fields are single-wing, but the ventilation shaft is situated at the upper boundary of the mine field (Fig. 7).

In the flank (diagonal) layout for mine ventilation, one shaft is located in the center of the mine fields when the mine fields are two-winged, while the other shafts are on the flanks. If the mine fields are single-winged, then one shaft is located on one boundary of the mine field, and the second on the opposite boundary (Fig. 8).

Centrally offset arrangement of shafts

Fig. 7. Central layout of mine ventilation

Depending on the placement and purpose of the fans, the flank ventilation layout may be:

1) wing-based, when each wing is served by an independent fan;

Fig. 8. Flank layout of mine ventilation

2) district-based, when each district is served by an independent fan;

3) group-based, when one fan serves a group of districts, but not the entire wing.

Fig. 9. Central layout of district ventilation

In the ventilation of extraction districts, depending on the point at which the ventilation stream enters and exits the districts, two principal ventilation layouts for districts should also be distinguished: central and flank (diagonal) (Figs. 9, 10).

Fig. 10. Flank layout of district ventilation

With the central scheme of ventilation of extraction areas, the points of entry and exit of the ventilation current from the areas are located on one line in the center of the extraction areas, if the extraction areas are double-winged, and on one of the boundaries of the extraction areas, if the extraction areas are single-winged (Fig. 9).

With the flank (diagonal) scheme of ventilation of areas, the point of entry of the ventilation current is located in the center of the extraction areas, and the exit points are on the boundaries of the extraction areas, if the extraction areas are double-winged. When the extraction areas are single-winged, the points of entry of the ventilation current are located on one boundary of the extraction areas, and the exit points on the other boundary of the extraction areas (Fig. 10).

In addition to the two basic schemes of ventilation of mines and extraction areas, there exist varieties and combinations of these ventilation schemes.

Central schemes of ventilation of mines, extraction areas, and their varieties are characterized by the fact that the ventilation current, after washing the working faces, returns again to the center of the mine fields or extraction areas in double-winged mine fields and extraction areas, or to the line of the point of entry of the ventilation current in single-winged mine fields and extraction areas (Figs. 6, 7, 9).

With the flank (diagonal) scheme of ventilation of mines, extraction areas, and their varieties, the ventilation current, after washing the working faces, does not return back, but goes to the boundaries of the mine fields and extraction areas when they are double-winged, and to the opposite boundary when the mine fields and extraction areas are single-winged (Figs. 8, 10). Consequently, the path of air movement with the central scheme is twice as great, and the maximum possible depression will also be greater.

5. The Concept of a Mine Ventilation System

In Russian, a system is understood as a whole made up of component parts, an order determined by the correct, regular arrangement of parts in a definite relation [5, 192]. Therefore, a mine ventilation system should be understood as the aggregate of the basic elements of ventilation, i.e., the method and scheme of ventilation, which characterize the ventilation of a mine as a whole.

6. Classification of Mine Ventilation Systems

From the point of view of ventilation, mines may constitute a single ventilation system or, owing to the large dimensions of the mine, consist of several sections that are independent with respect to ventilation. On the basis of the concept of a ventilation system established above, it follows that there may be two basic ventilation systems (Fig. 11 and the table):

1. A unified ventilation system, when, according to ventilation conditions, the mine is not divided into sections and the mine has one method and one scheme of ventilation.

2. A sectional ventilation system, when, according to ventilation conditions, the mine is divided into several sections that are independent with respect to ventilation. In each section there may be its own method and its own scheme of ventilation.

In addition to the two basic ventilation systems, there may exist combined systems, i.e., systems consisting of elements that characterize the unified and sectional ventilation systems.

Fig. 11. Classification of mine ventilation systems.

Conventional designations:

NSV—forcing method of ventilation,
VSV—exhaust method of ventilation,
NVSV—forcing-and-exhaust method of ventilation,
TsS—central ventilation layout,
FS—flank ventilation layout.

7. Conclusions

From what has been set forth above it follows:

1. The proposed terminology correctly reflects the ventilation processes occurring in a mine and fully corresponds to the concepts of method, layout, and system in the Russian language; moreover, there is an interrelationship among all the terms (ventilation, method of ventilation, ventilation layout, and ventilation system).

2. Establishing a unified formulation of the terms: ventilation, method of ventilation, ventilation layout, and ventilation system makes it possible to classify them (see the table).

3. Without a classification of ventilation layouts for working districts, it is difficult to establish rational ventilation layouts for mines.

4. The proposed classification of methods, layouts, and systems of ventilation considerably facilitates establishing the field of application both of the principal methods, layouts, and systems of ventilation and of their varieties, which is of exceptional importance in ventilation design.

5. Modern mine ventilation design must be based on a deep and comprehensive analysis of methods, layouts, and systems of ventilation, especially in the development of mineral deposits that are gas-bearing, liable to spontaneous combustion, and dangerous with respect to dust explosions; and this cannot be done without having their classification.

Establishing the field of application of the principal methods, layouts, and systems of ventilation is considerably easier than that of their varieties and combinations; and the conclusions of the analysis for the principal methods, layouts, and systems of ventilation may be extended, with appropriate corrections, to their varieties and combinations.

LITERATURE

1. Kovalev A. E., Voronina L. D. Mine Ventilation, Ugletekhizdat, 1951.
2. Batalin S. A. Ventilation of Kuzbass Mines, Ugletekhizdat, 1951.
3. Skochinsky A. A., Komarov V. B. Mine Ventilation, Ugletekhizdat, 1951.
4. Pravdenko D. Ya. Ventilation and Lighting of Mines, Fire Fighting, and Mine-Rescue Work, Ugletekhizdat, 1945.
5. Explanatory Dictionary of the Russian Language, 1940.
6. Skochinsky A. A. Mine Atmosphere, 1932.