On the Application of District (Sectional) Ventilation in Coal Mines of the Kuznetsk Basin
Abstract Generated abstract
This paper examines the need for district or sectional ventilation in gassy coal mines of the Kuznetsk Basin, where increasing seam gas emissions with depth require large air quantities and can produce excessive mine depression. Using ventilation resistance formulas, standard mine working dimensions, hoisting shaft calculations, permissible air velocities, and comparative schemes for shaft placement and central versus flank ventilation, the study evaluates the capacity of shafts, crosscuts, and other workings for mines of varying output and gas abundance. The analysis concludes that existing standard shaft and main crosscut sections often necessitate sectional ventilation, especially above modest production and gas thresholds, while other workings generally pass the required air. It further finds that larger ventilation sections are obtained with a two-wing mine, flank ventilation, and the specified intake shaft arrangement, and that stricter depression limits for seams prone to spontaneous combustion make sectional ventilation necessary at lower gas emissions.
Full Text
On the Application of District (Sectional) Ventilation in Coal Mines of the Kuznetsk Basin
A. F. Karataev
General Remarks
All coal mines of the Kuznetsk Basin are gassy. The exception is made up of mines developing coal seams down to a depth of 50–70 m from the surface: they are not gassy.
From the summary graph of the quantity of air subject to delivery into a mine, as a function of the mine’s daily output (Fig. 1), it is evident that
Fig. 1. Summary graph of the quantity of air subject to delivery into a mine, as a function of the mine’s daily output.
the principal factor determining this quantity of air is the gas emission of the seams.
In the coal mines of the Kuznetsk Basin, an increase in the gas emission of seams with depth is observed, in connection with which it becomes necessary to deliver very large quantities of air into the mines (Table 1).
The total depression of a mine is determined by the formula:
\[ h = R \cdot Q^2, \tag{1} \]
where \(R\) is the total resistance of the mine, and \(Q\) is the quantity of air subject to delivery into the mine, in cubic m/sec.
Table 1
Amount of air to be supplied to the mine, in \(m^3/sec\), depending on gas abundance
| Daily output of the mine, in \(t\) | \multicolumn{8}{c}{Methane gas emission, in \(m^3\) per 1 \(t\) of daily output} |
|---:|---:|---:|---:|---:|---:|---:|---:|---:|
| | 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 |
| | \multicolumn{8}{c}{Amount of air supplied to the mine, in \(m^3/sec\)} |
| 1000 | 25 | 31.3 | 37.5 | 46.4 | 58.0 | 69.6 | 81.2 | 92.8 |
| 2000 | 50 | 62.5 | 75.0 | 93.0 | 116.0 | 139.0 | 162.0 | 185.0 |
| 3000 | 75 | 94.0 | 113.0 | 139.0 | 174.0 | 209.0 | 244.0 | 278.0 |
| 4000 | 100 | 125.0 | 150.0 | 185.0 | 232.0 | 278.0 | 325.0 | 370.0 |
| 5000 | 125 | 156.0 | 187.0 | 232.0 | 290.0 | 348.0 | 405.0 | 462.0 |
| 6000 | 150 | 187.0 | 225.0 | 278.0 | 348.0 | 418.0 | 486.0 | 555.0 |
| 7000 | 175 | 218.0 | 263.0 | 335.0 | 405.0 | 485.0 | 568.0 | 648.0 |
| 8000 | 200 | 250.0 | 300.0 | 370.0 | 463.0 | 555.0 | 650.0 | 740.0 |
| 9000 | 225 | 282.0 | 337.0 | 416.0 | 520.0 | 625.0 | 730.0 | 830.0 |
| 10000 | 250 | 313.0 | 375.0 | 464.0 | 586.0 | 693.0 | 812.0 | 928.0 |
The amount of air to be supplied to the mine enters formula (1) as a square; this leads to a considerable increase in depression as \(Q\) increases.
Example. The daily output of mine \(A = 5000\ t\), the relative gas abundance \(Q_{om} = 15\ m^3\) per \(t\) of daily output, the amount of air to be supplied to the mine \(Q = 187\ m^3/sec\) (Table 1), and the specific resistance of the mine \(R = 0.013\) (easy ventilation).
Then the total depression of the mine will be
\[ h = R \cdot Q^2 = 0.013 \cdot 187^2 = 455 \ \text{mm water column}. \]
This indicates that, in order to supply the amount of air required by the gas abundance to this mine, the total mine depression must be greater than the maximum permissible value of \(300\ \text{mm}\) water column.
The total depression of a mine, under the existing rational ventilation scheme, can be reduced by: 1) reducing the resistance of the mine by increasing the cross-section of mine workings; 2) introducing sectional ventilation, when the mine as a whole is divided into a number of districts with an independent ventilation system.
The resistance of mine workings is determined by the formula:
\[ R = \alpha \frac{L \cdot P}{S^3}, \tag{2} \]
where \(\alpha\) is the coefficient of friction, \(L\) is the length of the working in \(m\), \(P\) is the perimeter of the working in \(m\), and \(S\) is the area of the cross-section of the working in sq. \(m\).
For trapezoidal workings, \(P = 4.16\sqrt{S}\). Substituting this value into formula (2), we obtain:
\[ R = \alpha \frac{L \cdot 4.16\sqrt{S}}{S^3} \quad \text{or} \quad R = \alpha \frac{4.16L}{S^{2.5}}, \tag{3} \]
from which it is evident that a slight increase in the area of the cross-section of a working sharply reduces its resistance; however, increasing the cross-section of a working leads to an increase in rock pressure on the working, which creates great difficulties in maintaining it.
The implementation of sectional ventilation of a mine requires the driving of additional shafts.
In order to judge the expediency of sectional ventilation, let us analyze the standard cross-sections of mine workings existing in the Kuznetsk Basin.
Analysis of Standard Cross-Sections of Mine Workings
In the development of coal deposits, production workings are at the same time also ventilation workings: they are used to supply fresh air to the place of work [1, 389].
The analysis of standard cross-sections of mine workings will consist in determining the cross-section according to the freight flow, depending on the purpose of the mine working, and in checking these cross-sections from the conditions of the maximum permissible velocity of air movement through them, i.e., from the conditions of ventilation.
We shall assume the opening of the mine field by vertical shafts with level crosscuts, as the most widespread method of opening deposits in the Kuznetsk Basin.
Analysis of the Cross-Section of the Hoisting Shaft
Under any scheme of mine ventilation, the hoisting shaft (skip or cage), serving for bringing the useful mineral to the surface, is used for ventilation: through it air enters the underground workings or is discharged from the mine to the surface.
In the Kuznetsk Basin, the cross-section of mine shafts is most often taken as circular. Concrete is used as the support material. This material has practically wide application, since it ensures the reliability of the support under any properties of the rocks and magnitude of rock pressure. The service life of such mine shafts is very considerable, owing to which the shafts serve for more than 20 years, providing a normal operating regime and requiring no repair. When sinking shafts of circular form, the greatest simplicity of work in extracting the rock is achieved. For equal cross-sectional areas, circular shafts offer less resistance to air movement than rectangular ones. The ratio of the total cross-sectional area of a circular mine shaft to the useful area is 30% greater than for a rectangular form of section. In gaseous mines, the cross-section of shafts according to ventilation conditions often turns out to be larger than according to the freight flow.
In analyzing the cross-section of the hoisting shaft, in the following exposition we shall consider only the circular form of shaft section. First, we calculate the cross-section of the hoisting shaft according to the freight flow for a daily mine output \(A\) from 1000 to 10000 tons and a depth from 100 to 1000 m.
We determine the minimum duration of one hoist from the conditions of permissible maximum accelerations, decelerations, and hoisting speeds. We take skip hoisting, with a skip unloading through the bottom. The acceleration \(j_1\) and deceleration \(j_3\) are taken equal, i.e.,
\[ j_1 = j_3 = 1\ \text{m/sec}^2. \]
We determine the hoisting height by the formula
\[ H = H_1 + H_2 + H_3 + H_4, \tag{4} \]
where \(H_1\) is the depth of the mine to the working horizon in m, \(H_2\) is the height of the underground bunker in m, \(H_3\) is the height of the surface bunker in m, \(H_4\) is the elevation of the skip frame above the edge of the bunker in m.
For the first horizon with a depth of 100 m, the hoisting height will be
\[ H = H_1 + H_2 + H_3 + H_4 = 100 + 15 + 12 + 3 = 130. \]
The maximum permissible hoisting speed is determined by the formula
\[ V_{\max}=0.8\sqrt{H}, \tag{5} \]
where \(H\) is the height of hoisting in m
\[ V_{\max}=0.8\sqrt{H}=0.8\sqrt{130}=9.1\ \text{m/sec}. \]
We shall determine the minimum duration of one hoisting operation from the speed diagram (Fig. 2).
Fig. 2. Speed diagram of skip hoisting.
Duration of the acceleration period:
\[ t_1=\frac{V_{\max}}{j_1}=\frac{9.1}{1}=9.1\ \text{sec}. \tag{6} \]
Duration of the retardation period:
\[ t_3=\frac{V_{\max}}{j_3}=\frac{9.1}{1}=9.1\ \text{sec}. \tag{7} \]
Distance traveled by the hoisting vessel during acceleration:
\[ x_1=\frac{1}{2}t_1V_{\max}=\frac{9.1}{2}\cdot 9.1=41.5\ \text{m}. \tag{8} \]
Distance traveled by the hoisting vessel during retardation:
\[ x_3=\frac{1}{2}t_3V_{\max}=\frac{9.1}{2}\cdot 9.1=41.5\ \text{m}. \tag{9} \]
Distance traveled by the hoisting vessel during the period of uniform hoisting:
\[ x_2=H-(x_1+x_3)=130-(41.5+41.5)=47\ \text{m}. \tag{10} \]
Duration of the period of uniform hoisting
\[ t_2=\frac{x_2}{V_{\max}}=\frac{47}{9.1}=5.2\ \text{sec}. \tag{11} \]
Duration of one hoisting operation
\[ T=t_1+t_2+t_3=9.1+5.2+9.1\simeq 24\ \text{sec}. \tag{12} \]
We determine the economy of the hoisting installation.
The average hoisting speed for the adopted parameters is
\[ V_{\text{avg}}=\frac{H}{T}=\frac{130}{24}=5.42\ \text{m/sec}. \tag{13} \]
Speed multiplier:
\[ \alpha=\frac{V_{\max}}{V_{\mathrm{av}}}=\frac{9.1}{5.42}=1.68. \tag{14} \]
For economical skip hoisting, \(\alpha\) should be equal to 1.1–1.3. Consequently, adopting the hoisting speed according to the formula \(V_{\max}=0.8\sqrt{H}\) gives an uneconomical hoisting installation. Taking the hoisting speed equal to half the maximum permissible speed, i.e.,
\[ V'_{\max}=0.5 V_{\max}=0.5\cdot 9.1 \simeq 4.5\ \text{m/sec}, \]
we carry out a recalculation.
Duration of the acceleration period:
\[ t_1=\frac{V'_{\max}}{j_1}=\frac{4.5}{1}=4.5\ \text{sec}. \]
The distance traveled by the hoisting vessel during acceleration,
\[ x_1=\frac{1}{2}t_1\cdot V'_{\max}=\frac{4.5}{2}4.5=10.1\ \text{m}. \]
The distance traveled by the hoisting vessel during retardation,
\[ x_3=\frac{1}{2}t_3 V'_{\max}=\frac{4.5}{2}4.5=10.1\ \text{m}. \]
The distance traveled by the hoisting vessel during the period of uniform motion,
\[ x_2=H-(x_1+x_3)=130-(10.1+10.1)=109.8\ \text{m}. \]
Duration of the period of uniform motion
\[ t_2=\frac{x_2}{V'_{\max}}=\frac{109.8}{4.5}=24.4\ \text{sec}. \]
Duration of one hoist
\[ T=t_1+t_2+t_3=4.5+24.4+4.5\simeq 34\ \text{sec}. \]
Let us check the economy of the hoisting installation:
\[ V_{\mathrm{av}}=\frac{H}{T}=\frac{130}{34}=3.83\ \text{m/sec}, \]
\[ \alpha=\frac{V'_{\max}}{V_{\mathrm{av}}}=\frac{4.5}{3.83}=1.18. \]
\(\alpha<1.3\); consequently, the hoisting installation, with the assumptions adopted above, has become economical.
The total time of one hoist
\[ T_1=T+\Theta, \tag{15} \]
where \(\Theta\) is the pause, i.e., the time required for loading and unloading the hoisting vessel,
\[ T_1=T+\Theta=34+10=44\ \text{sec}. \]
In the same way we calculate the time of one hoist for depths down to 1000 m at intervals of 100 m; the calculation results are summarized in Table 2.
Table 2. Duration of one hoist and values of the load delivered in one hoist
| Mine depth, m | Hoist height, m | Hoist speed, m/sec | Total time of 1 hoist, sec | 1000 | 2000 | 3000 | 4000 | 5000 | 6000 | 7000 | 8000 | 9000 | 10000 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mine depth, m | Hoist height, m | Hoist speed, m/sec | Total time of 1 hoist, sec | \multicolumn{10}{c}{Value of the load delivered in one hoist, in tons / Daily mine output, in tons} | |||||||||
| 100 | 130 | 4.5 | 44 | 1.00 | 2.00 | 3.00 | 4.00 | 5.00 | 6.00 | 8.00 | 8.00 | 9.00 | 10.00 |
| 200 | 230 | 6.0 | 55 | 1.30 | 2.50 | 3.80 | 5.00 | 6.30 | 7.60 | 10.10 | 10.00 | 11.40 | 12.70 |
| 300 | 330 | 7.0 | 64 | 1.50 | 3.00 | 4.40 | 5.90 | 7.30 | 8.75 | 11.70 | 11.70 | 13.20 | 14.60 |
| 400 | 430 | 8.0 | 72 | 1.70 | 3.30 | 5.00 | 6.60 | 8.30 | 9.80 | 13.10 | 13.10 | 14.80 | 16.50 |
| 500 | 530 | 9.0 | 78 | 1.80 | 3.60 | 5.40 | 7.20 | 8.90 | 10.60 | 14.30 | 14.30 | 16.00 | 17.80 |
| 600 | 630 | 10.0 | 84 | 1.90 | 3.90 | 5.70 | 7.60 | 9.50 | 11.40 | 15.20 | 15.20 | 17.10 | 19.00 |
| 700 | 730 | 10.5 | 90 | 2.00 | 4.20 | 6.30 | 8.30 | 10.50 | 12.40 | 16.60 | 16.60 | 18.60 | 20.70 |
| 800 | 830 | 11.5 | 94 | 2.10 | 4.40 | 6.60 | 8.80 | 10.80 | 13.10 | 17.30 | 17.30 | 19.50 | 21.50 |
| 900 | 930 | 12.0 | 99 | 2.20 | 4.60 | 6.90 | 9.10 | 11.40 | 13.70 | 18.20 | 18.20 | 20.40 | 22.60 |
| 1000 | 1030 | 13.0 | 102 | 2.30 | 4.80 | 7.20 | 9.40 | 11.80 | 14.20 | 18.60 | 18.60 | 21.20 | 23.50 |
We determine the value of the load delivered in one hoist for a mine with a daily output \(A = 1000\) t, a depth of 100 m, a hoist height \(H = 130\) m, and a duration of one hoist \(T_1 = 44\) sec.
Hourly output of the mine
\[ A_{\mathrm{h}}=\frac{A\cdot k}{t}, \tag{16} \]
where \(A\) is the daily output of the mine in t, \(k\) is the coefficient of irregularity, and \(t\) is the number of hours of hoist operation per day.
\[ A_{\mathrm{h}}=\frac{A\cdot k}{t}=\frac{1000\cdot 1.15}{14}=82.1\ \text{t}. \]
Number of hoists per hour
\[ n=\frac{3600}{T_1}=\frac{3600}{44}=82. \tag{17} \]
Value of the load delivered in one hoist
\[ G=\frac{A_{\mathrm{h}}}{n}=\frac{82.1}{82.0}=1\ \text{t}. \tag{18} \]
We likewise calculate the value of the load delivered in one hoist for depths up to 1000 m at intervals of 100 m and for daily mine outputs up to 10000 t at intervals of 1000 t. The result of the calculation is summarized in Table 2.
Using the data of Table 2, we construct a graph of the maximum value of the load delivered in one hoist as a function of the depth and daily output of the mine (Fig. 3). Along the abscissa axis we plot the value of the load hoisted at one time, in tons, and along the ordinate axis—the daily output of the mine, in tons.
We calculate the cross section of the hoisting shaft from the condition of the permissible velocity of air movement along the shaft. The quantity of air that can be passed through a specified shaft cross section is determined by the formula
\[ Q_{\mathrm{sec}}=S\cdot V\cdot \varphi, \tag{19} \]
where \(Q_{\mathrm{sec}}\) is the quantity of air to be supplied to the mine, in \(\text{m}^3/\text{sec}\); \(S\)—
the cross-sectional area of the shaft in m², \(V\) is the permissible velocity of air movement in m/sec, \(\varphi\) is the coefficient of useful\(^{1)}\) cross section of the shaft.
For a circular shaft,
\[ S=\frac{\pi D^{2}}{4}\quad \text{or}\quad S=0.785D^{2}, \tag{20} \]
where \(D\) is the diameter of the mine shaft in m.
Fig. 3. Graph of the quantity of load to be hoisted in one lift as a function of the daily productivity of the mine and its depth
Substituting the value of \(S\), expressed through \(D\), into formula (19), we obtain
\[ Q_{\text{sec}}=0.785\cdot D^{2}\cdot V\cdot \varphi, \]
whence
\[ D^{2}=\frac{Q_{\text{sec}}}{0.785\,V\cdot\varphi}. \]
For \(V=8\) m/sec and \(\varphi=0.85\),
\[ D^{2}=\frac{Q_{\text{sec}}}{0.785\cdot 8\cdot 0.85}=\frac{Q_{\text{sec}}}{5.32}, \]
\[ D=\frac{1}{\sqrt{5.32}}\sqrt{Q_{\text{sec}}}, \]
\[ D=0.432\sqrt{Q_{\text{sec}}}. \tag{21} \]
For a mine with a daily productivity of \(A=5000\) t, into which it is necessary to supply 1 m³/min of air per 1 t of output (relative gas abundance of 5 m³ per 1 t of output), according to Table 1 \(Q_{\text{sec}}=125\) m³/sec. The shaft diameter at this mine will be:
\[ D=0.432\sqrt{Q_{\text{sec}}}=0.432\sqrt{125}=0.432\cdot 11.2=4.85\text{ m}. \]
Similarly, we carry out the calculation of shaft diameters for mines with a daily productivity from 1000 to 10000 t and a relative gas abundance from 5 to 40 m³ per 1 t of output. The results of the calculation are summarized in Table 3.
\(^{1)}\) The clear opening inside the support, taking reinforcement into account.
Table 3. Shaft diameters determined by the quantity of air to be supplied to the mine, depending on its gas abundance
| Daily output of the mine, t | 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 |
|---|---|---|---|---|---|---|---|---|
| Methane gas emission in m³ per 1 t of daily output | Methane gas emission in m³ per 1 t of daily output | Methane gas emission in m³ per 1 t of daily output | Methane gas emission in m³ per 1 t of daily output | Methane gas emission in m³ per 1 t of daily output | Methane gas emission in m³ per 1 t of daily output | Methane gas emission in m³ per 1 t of daily output | Methane gas emission in m³ per 1 t of daily output | |
| Shaft diameters in m | Shaft diameters in m | Shaft diameters in m | Shaft diameters in m | Shaft diameters in m | Shaft diameters in m | Shaft diameters in m | Shaft diameters in m | |
| 1000 | 2.17 | 2.43 | 2.65 | 2.95 | 3.30 | 3.62 | 3.9 | 4.18 |
| 2000 | 3.05 | 3.43 | 3.75 | 4.18 | 4.65 | 5.10 | 5.5 | 5.9 |
| 3000 | 3.75 | 4.20 | 4.60 | 5.10 | 5.70 | 6.25 | 6.75 | 7.2 |
| 4000 | 4.32 | 4.90 | 5.30 | 5.90 | 6.60 | 7.20 | 7.80 | 8.3 |
| 5000 | 4.85 | 5.40 | 5.90 | 6.60 | 7.35 | 8.10 | 8.70 | 9.3 |
| 6000 | 5.30 | 5.90 | 6.50 | 7.20 | 8.10 | 8.85 | 9.55 | 10.2 |
| 7000 | 5.70 | 6.35 | 7.00 | 7.90 | 8.70 | 9.55 | 10.30 | 11.1 |
| 8000 | 6.12 | 6.82 | 7.50 | 8.35 | 9.30 | 10.20 | 11.10 | 11.8 |
| 9000 | 6.50 | 7.25 | 7.90 | 8.80 | 9.30 | 11.00 | 11.70 | 12.3 |
| 10000 | 6.85 | 7.65 | 8.35 | 9.35 | 10.40 | 11.40 | 12.40 | 13.1 |
Using the data of Table 3, we construct a graph of the dependence of shaft diameters on the daily output and gas abundance of the mine (Fig. 4). Along the abscissa axis we lay off the shaft diameters, and along the ordinate axis—the daily output of the mines.
In the coal industry of the USSR, two types of shaft cross sections are used for skip hoisting [2; 225].
Fig. 4. Graph of the dependence of mine-shaft diameters on daily output and gas abundance.
Type I—circular cross section of shafts, with two skips and a ladder compartment. Shaft diameters 4.5; 5.0 and 5.5 m; skip capacity: 4; 6 and 8 t (Fig. 5).
Type X—circular cross section of shafts, four skips. Shaft diameters 6.0; 6.0 and 6.5 m; skip capacity 4; 6 and 8 t (Fig. 6).
On the graph of the quantities of load to be hoisted in one hoist, Fig. 3, where the quantities of the hoisted load \(G\) are plotted along the \(x\)-axis, and the daily outputs of the mines \(A\) along the \(y\)-axis, perpendiculars are erected from the points 4, 6 and 8. These points correspond to the standard capacities of skips. The points of intersection of these perpendiculars with the lines issuing from the origin will indicate for what daily output of a mine the given skip is suitable, and, accordingly, the standard shaft section as well.
On the basis of graph 3 it is possible, without additional calculations, to establish:
1) the carrying capacity for the freight flow of shaft cross sections of type I and type X;
2) shaft cross section type X, with shaft diameters of 6.6 and 6.5 m and skip capacities of 4, 6, and 8 t, provides, from the same depths as type I, twice the output, because it has two pairs of skips. This is evident from the graph (Fig. 3) if perpendiculars are erected from the points 8, 12, 16, corresponding to the capacity of two pairs of skips.
If, on the graph of the dependence of mine-shaft diameters on daily output and gas abundance of mines (Fig. 4), where shaft diameters are plotted along the \(x\)-axis and daily outputs of mines along the \(y\)-axis, from the points 4.5; 5.0; 5.5; 6.0 and 6.5 lying on the \(x\)-axis and corresponding to the diameters of standard shaft cross sections, perpendiculars are erected, then the points of intersection of these perpendiculars with the curves issuing from the origin will indicate the daily outputs of mines to which the given shaft diameters correspond under ventilation conditions (i.e., the permissible velocity of air movement through the shaft), depending on the gas abundance of the mine.
Fig. 5. Typical cross section of a mine shaft.
Fig. 6. Typical cross section of a mine shaft.
For a clear comparison of the correspondence of a mine-shaft cross section to the freight flow and to ventilation, we construct a combined graph (Fig. 7) of the carrying capacity of the shaft for freight flow and for ventilation. According to statistical data, it may be assumed that, under the conditions of the Kuznetsk Basin, the first 50 m of depth do not yield gas, and each subsequent 100 m of depth gives an increase in gas abundance of 5 m³ per 1 t of daily output. Consequently, the limiting gas abundance of 40 m³ per 1 t of daily output will be at a depth
\[ \frac{40}{5}\cdot 100 + 50 = 850 \text{ m} \]
from the surface. Along the \(x\)-axis we plot the depth of the mine to which the adopted shaft cross section provides the required daily output of the mine, and along the \(y\)-axis the daily output of the mine. To construct the combined graph we use the graphs of Figs. 3 and 4.
From the combined graph (Fig. 7) it is evident that for gaseous mines the determining factor for the cross section of the shaft is gas abundance, i.e., the cross section of the shaft is determined not by the freight flow but by ventilation conditions. The exact cross section of the shaft of a gaseous mine is determined by the quantity of air to be supplied to the mine, depending on the gas emission of the seams being worked.
The cross section of shafts selected according to ventilation conditions for gaseous mines fully provides the required freight flow, and only
shaft cross-section type I with a shaft diameter of 4.5 m down to a depth of 450 m and a daily mine output of more than 2300 t is determined by the haulage flow.
When opening up a deposit with one pair of shafts (hoisting and ventilation), shaft cross-section type I provides, depending on gas abundance: with a shaft diameter of 5.5 m, a daily mine output of
Fig. 7. Graph of shaft capacity by haulage flow and ventilation.
6400 t from a depth of 150 m and 1700 t from a depth of 850 m; with a shaft diameter of 5.0 m, a daily mine output of 5200 t from a depth of 150 m and 1400 t from a depth of 850 m; with a shaft diameter of 4.5 m, from a depth of 130 m a daily mine output of 4300 t and from a depth of 850 m—1200 t.
To provide the daily outputs of mines in other ranges, opening up must be carried out not with one pair of shafts, or increased shaft diameters must be adopted.
Shaft cross-section type X is unacceptable for gassy mines. The concentration of a large haulage flow in one shaft leads, under ventilation conditions, to the need to lay an additional shaft to supply the mine with the required quantity of air. The structural complexity of constructing type X shafts and pit bottoms determined by this type, and the difficulty of organizing work during the period of construction and operation, also indicate the unacceptability of using this type of shaft when opening a mine field with one pair of shafts and, consequently, in such cases the use of sectional ventilation of mines appears absolutely necessary. This conclusion of ours is confirmed by Order No. 53 of the Ministry of the Coal Industry of the Eastern Regions of the USSR of March 31, 1947, according to which the principal types of mine construction
in 1947–48 will be 1000, 2000, 3000, 4000 and 5000 t of daily output. These outputs have already been mastered in the practice of the Kuznetsk Basin.
We shall analyze the standard cross-sections of shafts of type I for the indicated daily outputs of mines.
According to the graph of the capacity of shafts in terms of cargo flow and ventilation (Fig. 7), we have the following:
A shaft cross-section of type I with a diameter of 5.5 m, under ventilation conditions (gas abundance), provides the daily output of a mine as follows:
| Daily output | From a depth of |
|---|---|
| 5000 t | 270 m |
| 4000 t | 375 m |
| 3000 t | 530 m |
| 2000 t | 750 m |
In terms of cargo flow, this shaft cross-section provides the daily output:
| Daily output | From a depth of |
|---|---|
| 5000 t | 370 m |
| 4000 t | 650 m |
A shaft cross-section of type I with a diameter of 5.0 m, under ventilation conditions, provides the daily output of a mine as follows:
| Daily output | From a depth of |
|---|---|
| 5000 t | 170 m |
| 4000 t | 280 m |
| 3000 t | 430 m |
| 2000 t | 650 m |
In terms of cargo flow, this cross-section provides the daily output of a mine as follows:
| Daily output | From a depth of |
|---|---|
| 5000 t | 190 m |
| 4000 t | 310 m |
| 3000 t | 650 m |
A shaft cross-section of type I with a diameter of 4.5 m, under ventilation conditions, provides the daily output of a mine as follows:
| Daily output | From a depth of |
|---|---|
| 4000 t | 180 m |
| 3000 t | 300 m |
| 2000 t | 520 m |
In terms of cargo flow, this cross-section provides the daily output:
| Daily output | From a depth of |
|---|---|
| 4000 t | 100 m |
| 3000 t | 240 m |
| 2000 t | 600 m |
From the above it follows that the cross-section of shafts of type I is appropriate to the conditions of cargo flow and ventilation for depths up to 270–300 m: 1) with a shaft diameter of 5.5 m for a daily output of 5000 t; 2) with a shaft diameter of 5.0 m for a daily output of a mine of 4000 t; 3) with a shaft diameter of 4.5 m for a daily output of a mine of 3000 t.
A depth of 270–300 m corresponds to a mine with a gas abundance of 10 m³ per 1 t of daily output; consequently, the cross-section of shafts of type I is suitable, in terms of cargo-flow and ventilation conditions, for mines with a gas abundance of 10 m³ per 1 t of daily output. An increase in the gas abundance of mines leads to a significant divergence between the values of shaft diameters determined by cargo flow and by ventilation (Fig. 7).
Calculation of the Cross Section of a Ventilation Shaft
The cross section of a ventilation shaft is determined by the quantity of air to be supplied to the mine or exhausted from it. These shafts are equipped to provide auxiliary operations (the raising and lowering of people, materials, and equipment), and sometimes they serve only for the passage of air. The cross section of ventilation shafts and their number depend mainly on the adopted mine-ventilation scheme and, more precisely, on ensuring the permissible air velocity through them (according to the Technical Operating Rules).
Calculation of Standard Cross Sections of Horizontal Haulage Workings
The most widespread form of cross section for horizontal workings in the coal mines of the Kuznetsk Basin is trapezoidal, because timber is still used as the principal support material. In addition, the trapezoidal form is capable of taking vertical and lateral pressure. This form provides the fullest use of the cross section when equipment and means of transport are placed in it.
Where rocks are unstable and the service life is considerable, and where lateral rock pressure is significant, concrete support is used, and the form of the section is arched with straight walls.
In analyzing sections, we shall consider the trapezoidal form of section for horizontal workings and the arched form with a basket-handle arch.
The cross section of haulage horizontal workings is determined by the clearance dimensions of haulage vessels and electric locomotives, the number of rail tracks, and the method of movement of workers. The cross sections of workings obtained from these conditions are checked according to the quantity of air to be supplied to the mine through these workings, because in coal mines operating workings are at the same time ventilation workings.
In modern mines haulage is carried out by electric locomotives; therefore, in calculating the standard sections of haulage workings, the clearance dimensions of electric locomotives are taken as the basis, since they have larger dimensions than mine cars.
The results of the calculation of the cross section of standard haulage workings are summarized in Table 4.
Analysis of the Cross Section of the Main Crosscut under Ventilation Conditions
The cross section of the main crosscut is determined (as that of a horizontal haulage working) by freight flow and ventilation.
We calculate the magnitude of the cross section of the main crosscut for daily mine outputs from 1000 to 5000 t, because standard sections of type-I shafts, when a deposit is opened by one pair of shafts (hoisting and ventilation), cannot ensure a large daily mine output. This was established on the basis of the above analysis of standard sections of type-I shafts with respect to freight flow and ventilation.
When a deposit is opened by vertical shafts with level crosscuts (the principal method of opening deposits in the Kuznetsk Basin), the following four variants are possible for the location of the shaft supplying air to the mine:
Table 4. Cross-sectional areas of standard haulage workings, perimeters, and the quantity of air passing through the workings at an air-stream velocity of 8 m/sec
| Type of working | Shape of working | Wooden support: 1-t car, battery-electric locomotive, S | Wooden support: 1-t car, battery-electric locomotive, P | Wooden support: 1-t car, battery-electric locomotive, Q | Wooden support: 1-t car, trolley locomotive, S | Wooden support: 1-t car, trolley locomotive, P | Wooden support: 1-t car, trolley locomotive, Q | Wooden support: 2- and 3-t car, battery-electric locomotive, S | Wooden support: 2- and 3-t car, battery-electric locomotive, P | Wooden support: 2- and 3-t car, battery-electric locomotive, Q | Wooden support: 2- and 3-t car, trolley locomotive, S | Wooden support: 2- and 3-t car, trolley locomotive, P | Wooden support: 2- and 3-t car, trolley locomotive, Q | Concrete support: 1-t car, battery-electric locomotive, S | Concrete support: 1-t car, battery-electric locomotive, P | Concrete support: 1-t car, battery-electric locomotive, Q | Concrete support: 1-t car, trolley locomotive, S | Concrete support: 1-t car, trolley locomotive, P | Concrete support: 1-t car, trolley locomotive, Q | Concrete support: 2-t car, battery-electric locomotive, S | Concrete support: 2-t car, battery-electric locomotive, P | Concrete support: 2-t car, battery-electric locomotive, Q | Concrete support: 2-t car, trolley locomotive, S | Concrete support: 2-t car, trolley locomotive, P | Concrete support: 2-t car, trolley locomotive, Q | Concrete support: 3-t car, battery and trolley locomotives, S | Concrete support: 3-t car, battery and trolley locomotives, P | Concrete support: 3-t car, battery and trolley locomotives, Q |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Single-track | Trapezoidal | 4.30 | 8.4 | 34.1 | 4.5 | 9.00 | 36.0 | 4.83 | 8.92 | 38.6 | 5.6 | 9.5 | 44.8 | |||||||||||||||
| Single-track | Arched with box arch | 3.98 | 7.6 | 31.8 | 4.35 | 7.58 | 34.8 | 4.44 | 5.18 | 35.5 | 4.68 | 8.41 | 37.5 | 5.1 | 8.61 | 40.8 | ||||||||||||
| Two-track | Trapezoidal | 5.85 | 9.98 | 46.8 | 6.88 | 10.61 | 55.0 | 6.80 | 11.1 | 51.2 | 8.15 | 11.17 | 65.2 | |||||||||||||||
| At a haulage speed of up to 1.5 m/sec | Arched with box arch | 5.7 | 9.17 | 45.6 | 6.32 | 9.61 | 50.1 | 7.35 | 1.00 | 58.8 | 8.0 | 10.84 | 64.0 | 8.35 | 11.0 | 66.8 | ||||||||||||
| At a haulage speed of up to 1.5 m/sec | Trapezoidal | 6.70 | 10.88 | 53.6 | 7.93 | 11.54 | 63.5 | 7.8 | 11.98 | 62.3 | 9.20 | 12.2 | 73.5 | |||||||||||||||
| At a haulage speed of more than 1.5 m/sec | Arched with box arch | 7.27 | 9.32 | 58.2 | 7.85 | 10.71 | 62.8 | 8.98 | 11.56 | 71.8 | 9.7 | 11.93 | 77.5 | 10.1 | 12.16 | 80.8 |
on the footwall side of the deposit, a single-wing mine (Fig. 8, variant I),
between the seams, a single-wing mine (Fig. 8, variant III),
on the footwall side of the deposit, a two-wing mine (Fig. 8, variant II),
between the seams, a two-wing mine (Fig. 8, variant IV).
We determine the cross-sectional area of the main crosscut for a mine with a daily output of \(A = 5000\) t1, with a gas emission rate of \(5 \text{ m}^3\) per 1 t of daily production.
To simplify the analysis, we assume that the quantity of air to be supplied to the mine is distributed uniformly among the wings and seams.
Fig. 8. Diagrams of possible variants for the location of the shaft supplying air to the mine.
When the shaft supplying air to the mine is located on the footwall side of the deposit according to variant I (Fig. 8), the cross-sectional area of the main crosscut is determined by the formula:
\[ S_1 = \frac{Q_{\text{sec}}}{V}, \]
where \(S_1\) is the cross-sectional area of the main crosscut in \(\text{m}^2\), \(Q_{\text{sec}}\) is the quantity of air to be supplied to the mine (Table 1), and \(V\) is the permissible velocity of air movement through these workings in m/sec.
\[ S_1 = \frac{Q_{\text{sec}}}{V} = \frac{125}{8} = 15.65 \ \text{m}^2. \]
When the shaft supplying air to the mine is located between the seams according to variant III (Fig. 8), the cross-sectional area of the main crosscut is determined by the formula:
\[ S_{\mathrm{III}} = \frac{Q_{\text{sec}}}{2 \cdot V} = \frac{125}{2 \cdot 8} = 7.82 \ \text{m}^2. \]
When the shaft supplying air to the mine is located in the footwall according to variant II (Fig. 8), the cross-sectional area of the main crosscut is determined by the formula:
\[ S_{\mathrm{II}}=\frac{Q_{\mathrm{sec}}}{V}=\frac{125}{8}=15.65\ \mathrm{m}^2. \]
When the shaft supplying air to the mine is located between the seams according to variant IV (Fig. 8), the cross-sectional area of the main crosscut is determined by the formula:
\[ S_{\mathrm{IV}}=\frac{Q_{\mathrm{sec}}}{2\cdot V}=\frac{125}{2\cdot 8}=7.82\ \mathrm{m}^2. \]
We carry out an analogous calculation for other daily outputs of the mine and gas-abundance values, and summarize the calculation results in Table 5.
For analysis of the data in Table 5 we assume that the support of the main crosscut is concrete, the cross-sectional shape is arched with straight walls, and the cross-sectional area is the largest standard one, i.e. \(S=10.1\ \mathrm{m}^2\).
From Table 5 and Fig. 8 it is evident:
- In terms of ventilation conditions, the location of the shaft supplying air to the mine according to variants III and IV is equivalent and more rational in comparison with variants I and II.
For supplying the same quantity of air to the mine, the location of the shaft according to variants III and IV requires a cross-sectional area of the main crosscut two times smaller.
-
Variant III of the location of the shaft supplying air to the mine eliminates the shortcomings of a single-wing mine and, in terms of ventilation conditions, turns it, as it were, into a two-wing mine.
-
Variant II of the location of the shaft supplying air to the mine (especially with a long crosscut), in terms of ventilation conditions, loses the advantages of a two-wing mine and turns into a single-wing mine.
-
The maximum standard section of the main crosscut \(S=10.1\ \mathrm{m}^2\) provides air, under variants I and II of the location of the shaft supplying air to the mine, for a daily mine output of:
\[ \begin{aligned} A&=3000\ \mathrm{t} &&\text{with } Q_{ot}=5\ \mathrm{m}^3 \text{ per } 1\ \mathrm{t} \text{ of daily output},\\ A&=2000\ \mathrm{t} &&\text{'' } Q_{ot}=15\ \mathrm{m}^3 \text{ '' '' ''},\\ A&=1000\ \mathrm{t} &&\text{'' } Q_{ot}=35\ \mathrm{m}^3 \text{ '' '' ''.} \end{aligned} \]
Under variants III and IV of the location of the shaft supplying air to the mine, for a daily mine output of:
\[ \begin{aligned} A&=5000\ \mathrm{t} &&\text{with } Q_{ot}=10\ \mathrm{m}^3 \text{ per } 1\ \mathrm{t} \text{ of daily output},\\ A&=4000\ \mathrm{t} &&\text{'' } Q_{ot}=15\ \mathrm{m}^3 \text{ '' ''},\\ A&=3000\ \mathrm{t} &&\text{'' } Q_{ot}=20\ \mathrm{m}^3 \text{ ''},\\ A&=2000\ \mathrm{t} &&\text{'' } Q_{ot}=35\ \mathrm{m}^3 \text{ ''.} \end{aligned} \]
- The minimum standard section of the main crosscut \(S=4.0\ \mathrm{m}^2\) provides air, under variants I and II of the location of the shaft supplying air to the mine, for a daily mine output \(A=1000\ \mathrm{t}\) and with \(Q_{ot}=10\ \mathrm{m}^3\) per \(1\ \mathrm{t}\) of daily output; under variants III and IV of the location of the shaft supplying air to the mine, for a daily mine output \(A=2000\) with \(Q_{ot}=10\ \mathrm{m}^3\) per \(1\ \mathrm{t}\) of daily output.
The analysis we have carried out of the required cross section of the main crosscut under ventilation conditions for gassy mines shows that the cross section of the crosscut depends chiefly on the gas abundance of the mines and
Table 5. Cross-sectional areas of the main crosscut as a function of the daily output and gas abundance of the mine
| Daily output of the mine | Single-wing mine: gas abundance \(Q_{om}\) | Single-wing mine: first development variant \(S_I\) | Single-wing mine: third development variant \(S_{III}\) | Two-wing mine: gas abundance \(Q_{om}\) | Two-wing mine: second development variant \(S_{II}\) | Two-wing mine: fourth development variant \(S_{IV}\) |
|---|---|---|---|---|---|---|
| \(A = 5000\ m\) | 5 | 15.65 | 7.82 | 5 | 15.65 | 7.82 |
| \(A = 5000\ m\) | 10 | 19.50 | 9.75 | 10 | 19.50 | 9.75 |
| \(A = 5000\ m\) | 15 | 23.40 | 11.70 | 15 | 23.40 | 11.70 |
| \(A = 5000\ m\) | 20 | 29.00 | 14.50 | 20 | 29.00 | 14.50 |
| \(A = 5000\ m\) | 25 | 36.30 | 18.15 | 25 | 36.30 | 18.15 |
| \(A = 5000\ m\) | 30 | 43.50 | 21.75 | 30 | 45.50 | 21.75 |
| \(A = 5000\ m\) | 35 | 50.80 | 25.40 | 35 | 50.80 | 25.40 |
| \(A = 5000\ m\) | 40 | 57.80 | 28.90 | 40 | 57.80 | 28.90 |
| \(A = 4000\ m\) | 5 | 12.50 | 6.25 | 5 | 12.50 | 6.25 |
| \(A = 4000\ m\) | 10 | 16.00 | 8.00 | 10 | 16.00 | 8.00 |
| \(A = 4000\ m\) | 15 | 18.80 | 9.40 | 15 | 18.80 | 9.40 |
| \(A = 4000\ m\) | 20 | 23.20 | 11.60 | 20 | 23.20 | 11.60 |
| \(A = 4000\ m\) | 25 | 29.00 | 14.50 | 25 | 29.00 | 14.50 |
| \(A = 4000\ m\) | 30 | 34.80 | 17.40 | 30 | 34.80 | 17.40 |
| \(A = 4000\ m\) | 35 | 40.70 | 20.35 | 35 | 40.70 | 20.35 |
| \(A = 4000\ m\) | 40 | 46.40 | 23.20 | 40 | 46.40 | 23.20 |
| \(A = 3000\ m\) | 5 | 9.32 | 4.70 | 5 | 9.32 | 4.70 |
| \(A = 3000\ m\) | 10 | 11.90 | 5.85 | 10 | 11.90 | 5.85 |
| \(A = 3000\ m\) | 15 | 14.20 | 7.10 | 15 | 14.20 | 7.10 |
| \(A = 3000\ m\) | 20 | 17.40 | 8.70 | 20 | 17.40 | 8.70 |
| \(A = 3000\ m\) | 25 | 21.80 | 10.90 | 25 | 21.80 | 10.90 |
| \(A = 3000\ m\) | 30 | 26.20 | 13.10 | 30 | 26.20 | 13.10 |
| \(A = 3000\ m\) | 35 | 30.50 | 15.25 | 35 | 30.50 | 15.25 |
| \(A = 3000\ m\) | 40 | 34.80 | 17.40 | 40 | 34.80 | 17.40 |
| \(A = 2000\ m\) | 5 | 6.26 | 3.13 | 5 | 6.26 | 3.13 |
| \(A = 2000\ m\) | 10 | 7.80 | 3.90 | 10 | 7.80 | 3.90 |
| \(A = 2000\ m\) | 15 | 9.38 | 4.69 | 15 | 9.38 | 4.69 |
| \(A = 2000\ m\) | 20 | 11.60 | 5.80 | 20 | 11.60 | 5.80 |
| \(A = 2000\ m\) | 25 | 14.50 | 7.25 | 25 | 14.50 | 7.25 |
| \(A = 2000\ m\) | 30 | 17.40 | 8.70 | 30 | 17.40 | 8.70 |
| \(A = 2000\ m\) | 35 | 20.20 | 10.10 | 35 | 20.20 | 10.10 |
| \(A = 2000\ m\) | 40 | 23.20 | 11.60 | 40 | 23.20 | 11.60 |
| \(A = 1000\ m\) | 5 | 3.13 | 5 | 3.15 | ||
| \(A = 1000\ m\) | 10 | 3.92 | 10 | 3.92 | ||
| \(A = 1000\ m\) | 15 | 4.68 | 15 | 4.68 | ||
| \(A = 1000\ m\) | 20 | 5.80 | 20 | 5.80 | ||
| \(A = 1000\ m\) | 25 | 7.25 | 25 | 7.25 | ||
| \(A = 1000\ m\) | 30 | 8.70 | 4.35 | 30 | 8.70 | 4.35 |
| \(A = 1000\ m\) | 35 | 10.1 | 5.05 | 35 | 10.1 | 5.05 |
| \(A = 1000\ m\) | 40 | 11.6 | 5.80 | 40 | 11.6 | 5.80 |
to a considerable extent on the adopted method of opening, i.e., on the location of the shaft supplying air to the mine in relation to the suite of coal seams being worked.
The question of the cross section of the main crosscut of a gassy mine can be correctly resolved only with a clear understanding of the distribution of gas content among the seams and with a comprehensive solution of the question of mine ventilation and of opening the deposit.
Dimensions of Districts for Sectional Ventilation
The dimensions of a ventilation section, with the existing standard cross sections of mine workings, are determined from the condition of the maximum permissible depression. At present the maximum depression is taken to be \(h = 300\) mm water column. In mines working coal seams prone to spontaneous combustion, it is recommended that the maximum depression be taken as not more than \(h = 100\text{–}150\) mm water column.
Let us determine the dimensions of the ventilation section for a mine with a daily output \(A = 5000\) t, working a suite of seams. We take the thickness of each seam as \(2.5\) m, the gas emission as \(5\ \text{m}^3\) per 1 t of daily output, the ventilation scheme as central, and the arrangement of shafts according to variant IV (Fig. 8).
The quantity of air to be supplied to the mine is \(Q = 125\ \text{m}^3/\text{sec}\) (Table 1). With the adopted arrangement scheme for the shaft of the mine supplying air, the following amount of air will pass through the shaft:
\[ Q_{\text{shaft}} = Q = 125\ \text{m}^3/\text{sec}. \]
Through the crosscut:
\[ Q_{\text{cr}}=\frac{Q_{\text{shaft}}}{2}=\frac{125}{2}=62.5\ \text{m}^3/\text{sec}. \]
Through the group drift:
\[ Q_{\text{dr}}=\frac{Q_{\text{cr}}}{2}=\frac{62.5}{2}=31.75\ \text{m}^3/\text{sec}. \]
The output of the longwalls of one seam with thickness \(m = 2.5\) m, with daily advance \(a = 1.3\) m, inclined height of the level \(l = 100\) m, and volumetric weight of coal \(\gamma = 1.3\), will be
\[ A_{\text{lw}} = l \cdot m \cdot a \cdot \gamma = 100 \cdot 2.5 \cdot 1.3 \cdot 1.3 = 422\ \text{t}. \]
With a daily mine output \(A = 5000\) t and the adopted opening scheme, each group drift will serve extraction amounting to
\[ \frac{5000}{4}=1250\ \text{t}. \]
The number of seams simultaneously in operation will be
\[ n=\frac{1250}{A_{\text{lw}}}=\frac{1250}{422}=2.96. \]
We take three seams.
The calculated depression of the mine will be
\[ h = h_1 + h_2 + h_3 + h_4 + h_5 = 100\ \text{mm water column}, \]
where \(h_1\) is the depression of the shafts supplying and discharging air; \(h_2\) is the depression of the main crosscuts of the working and ventilation horizons; \(h_3\) is the depression of the group drifts of the working and ventilation horizons; \(h_4\) is the depression of the intermediate crosscuts of the working and ventilation horizons; \(h_5\) is the depression of the most remote extraction district. The calculation of depressions is summarized in Table 6.
Table 6
| No. of section of ventilation scheme | Name of working | $S$ | $S^2$ | $\sigma$ | $P$ | $\sigma \dfrac{P}{S^3}$ | $l$ | $Q$ | $Q^2$ | $h$ | $v$ | $\sigma \dfrac{LP}{S^3}$ | $Q$ | $h$ | $v$ | $\sigma \dfrac{LP}{S^3}$ | $Q$ | $h$ | $v$ |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1—2 | Hoisting shaft | 23.76 | 13300 | 0.0020 | 17.3 | 0.0000026 | 270 | 125 | 15600 | 10.90 | 5.28 | 0.000702 | 156 | 17 | 6.58 | 0.000702 | 187 | 24.5 | 7.8 |
| 2—3 | Main crosscut | 10.1 | 1030 | 0.0018 | 12.16 | 0.0000212 | 150 | 62.5 | 3900 | 12.40 | 6.25 | 0.00318 | 78 | 21.8 | 7.72 | 0.00318 | 93 | 27.4 | 9.2 |
| 3—4 | Group drift | 9.2 | 778 | 0.0018 | 12.62 | 0.0000292 | |||||||||||||
| 4—5 | Intermediate crosscut | 9.2 | 778 | 0.0018 | 12.62 | 0.0000292 | 20 | 31.75 | 1000 | 0.585 | 3.45 | 0.000585 | 34 | 0.676 | 3.70 | 0.000585 | 46.5 | 1.265 | 5.05 |
| 5—6 | Intermediate crosscut | 9.2 | 778 | 0.0018 | 12.62 | 0.0000292 | 20 | 21.1 | 445 | 0.260 | 2.30 | 0.000585 | 22.6 | 0.299 | 2.46 | 0.000585 | 31.1 | 0.562 | 3.37 |
| 6—7 | Intermediate crosscut | 9.2 | 778 | 0.0018 | 12.62 | 0.0000292 | 20 | 10.55 | 111.5 | 0.065 | 1.15 | 0.000585 | 11.3 | 0.075 | 1.23 | 0.000585 | 15.5 | 0.140 | 1.67 |
| 7—8 | Extraction section | 4.38 | 5.03 | 7.53 | |||||||||||||||
| 8—9 | Intermediate crosscut, ventilation horizon | 9.2 | 778 | 0.0018 | 12.62 | 0.0000292 | 20 | 10.55 | 111.5 | 0.065 | 1.15 | 0.000585 | 11.3 | 0.075 | 1.23 | 0.000585 | 15.5 | 0.140 | 1.67 |
| 9—10 | Intermediate crosscut, ventilation horizon | 9.2 | 778 | 0.0018 | 12.62 | 0.0000292 | 20 | 21.1 | 445 | 0.260 | 2.30 | 0.000585 | 22.6 | 0.299 | 2.46 | 0.000585 | 31.1 | 0.562 | 3.37 |
| 10—11 | Intermediate crosscut, ventilation horizon | 9.2 | 778 | 0.0018 | 12.62 | 0.0000292 | 20 | 31.75 | 1000 | 0.585 | 3.45 | 0.000585 | 34 | 0.676 | 3.70 | 0.000585 | 46.5 | 1.265 | 5.05 |
| 11—12 | Group drift, ventilation horizon | 9.2 | 778 | 0.0018 | 12.62 | 0.0000292 | |||||||||||||
| 12—13 | Main crosscut, ventilation horizon | 10.1 | 1030 | 0.0018 | 12.16 | 0.0000212 | 150 | 62.5 | 3900 | 12.40 | 6.25 | 0.00318 | 78 | 21.8 | 7.72 | 0.00318 | 93 | 27.4 | 9.2 |
| 13—14 | Ventilation shaft | 23.76 | 13300 | 0.0020 | 17.3 | 0.0000026 | 170 | 125 | 15600 | 6.90 | 5.28 | 0.000442 | 156 | 10.75 | 6.58 | 0.000442 | 187 | 15.45 | 7.8 |
| Without the group drift | 48.8 | 78.58 | 106.6 |
At a maximum mine depression of \(h = 100\) mm water column, the depression of the group drifts will be
\[ h_{3}=h-(h_{1}+h_{2}+h_{4}+h_{5})=100-48.8=51.2 \text{ mm water column}, \]
but at the same time
\[ h_{3}=R_{3}\cdot Q_{3}^{2}, \]
whence
\[ R_{3}=\frac{h_{3}}{Q_{3}^{2}}=\frac{51.2}{31.75^{2}}=0.0512. \]
The length of the ventilation section of one wing under the central scheme of mine ventilation is determined by the formula
\[ l=\frac{R_{3}}{2R}, \]
where \(R\) is the resistance of 1 running m of the group drift,
\[ l=\frac{R_{3}}{2R}=\frac{0.0512}{2\cdot 0.0000292}=880 \text{ m}, \]
for two wings—1760 m.
At a maximum mine depression of \(h = 150\) mm water column,
\[ h_{3}=h-(h_{1}+h_{2}+h_{4}+h_{5})=150-48.8=101.2 \text{ mm water column}. \]
\[ R_{3}=\frac{h_{3}}{Q_{3}^{2}}=\frac{101.2}{31.75^{2}}=0.1012. \]
The length of the ventilation section of one wing of the mine will be
\[ l=\frac{R_{3}}{2R}=\frac{0.1012}{2\cdot 0.0000292}=1735 \text{ m}, \]
for two wings—3470 m.
At a maximum mine depression of \(h = 300\) mm water column,
\[ h_{3}=h-(h_{1}+h_{2}+h_{4}+h_{5})=300-48.8=251.2 \text{ mm water column}. \]
\[ R_{3}=\frac{h_{3}}{Q_{3}^{2}}=\frac{251.2}{31.75^{2}}=2.512. \]
The length of the ventilation section of one wing of the mine will be
\[ l=\frac{R_{3}}{2R}=\frac{2.512}{2\cdot 0.0000292}=4300 \text{ m}, \]
for two wings—8600 m.
Analogously to the preceding cases, we calculate the lengths of ventilation sections for mines with gas emissions of 10 and 15 \(m^{3}\) per 1 ton of daily output, for the flank (diagonal) scheme of mine ventilation, and also for the arrangement of the shaft supplying air to the mine according to variant III (Fig. 8). The results of the calculation are summarized in Table 7.
Table 7 clearly shows the advantages of the flank scheme of ventilation for large mines, and also of a two-wing mine, from the standpoint of ventilation. In a single-wing mine, under the central scheme of ventilation, the ventilation section along the strike is obtained as half as large (820 m versus 1760) as in a two-wing mine, with almost the same depression.
Table 7. Dependence of the length of a ventilation section on gas abundance for a mine with a daily output of 5000 t
| Variant of location of the intake shaft | Ventilation scheme | I category, \(h=100\) | I category, \(h=150\) | I category, \(h=300\) | II category, \(h=100\) | II category, \(h=150\) | II category, \(h=300\) | III category, \(h=100\) | III category, \(h=150\) | III category, \(h=300\) |
|---|---|---|---|---|---|---|---|---|---|---|
| IV (Fig. 8) | Central ventilation scheme | 1760 | 3470 | 8600 | 634 | 2102 | 6540 | — | 688 | 3080 |
| IV (Fig. 8) | Flank ventilation scheme | 3520 | 6940 | 17200 | 1268 | 4204 | 13080 | — | 1376 | 6160 |
| III (Fig. 8) | Central ventilation scheme | 820 | 1675 | 4230 | 267 | 1000 | 3240 | — | 317 | 1500 |
| III (Fig. 8) | Flank ventilation scheme | 1640 | 3350 | 8460 | 534 | 2000 | 6480 | — | 634 | 3000 |
about 100 mm water column. The number of shafts will also be twice as large: 4 instead of 2. The use of the flank ventilation scheme in both cases doubles the size of the ventilation section along the strike (3520 m as against 1760, Table 7).
To open up a deposit along the strike for 6160 m by single-wing mines (according to variant III, Fig. 8), with sectional ventilation and a central ventilation scheme, the following will be required:
\[ n=\frac{L}{l}k=\frac{6160}{1500}\,2 \simeq 8 \text{ shafts,} \]
where \(n\) is the number of shafts required to open up the entire deposit; \(L\) is the length of the mine field along the strike, in m; \(l\) is the length of the ventilation section, in m (Table 7); \(k\) is the number of shafts in the section (with the central ventilation scheme we take two shafts in the section, and with the flank scheme—three shafts).
For a double-wing mine (variant IV, Fig. 8) and a central ventilation scheme,
\[ n=\frac{L}{l}k=\frac{6160}{3080}\,2=4 \text{ shafts.} \]
A transition to the flank ventilation scheme will require
\[ n=\frac{L}{l}k=\frac{6160}{6160}\,3=3 \text{ shafts.} \]
It follows from the foregoing that, under sectional ventilation, from the standpoint of ventilation, the mine supplying air must be laid out according to variant IV (Fig. 8), and the ventilation scheme should be adopted as the flank scheme.
Conclusions
On the basis of the analysis carried out above of the ventilation of large coal mines of the Kuznetsk Basin, it follows that:
- Standard cross-sections of mine workings, with a daily mine output of more than 500 t and a gas abundance of 10 m³ per 1 t of daily output, require, under ventilation conditions, a transition to sectional ventilation.
-
The transition to sectional ventilation is dictated mainly by the existing standard cross sections of shafts and main crosscuts. All other workings freely pass the required quantity of air without exceeding the permissible air velocity (Table 6).
-
The dimensions of a ventilation section along the dip are determined by the cross section of the shafts and do not exceed 270–300 m; consequently, for greater mine depths it is necessary to revise the existing standards for mine-shaft cross sections.
-
The dimensions of ventilation sections along the strike are determined by the maximum permissible overall mine depression, the arrangement of the shafts supplying air to the mine, the ventilation scheme, and the number of wings.
-
The greatest dimensions of ventilation sections, under ventilation conditions, are provided by the arrangement of the shaft supplying air to the mine according to variant IV (Fig. 8), by a two-wing mine, and by a flank ventilation scheme.
-
When mining coal seams prone to spontaneous combustion, where it is recommended that the mine depression be no more than 150 mm water column, the need to change over to sectional ventilation arises already at a gas abundance of \(Q_{om} = 10 \, m^3\) per 1 t of daily output, especially when the shaft supplying air to the mine is arranged according to variant III (Fig. 8), as is evident from Table 7.
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In a single-wing mine, even with a mine depression of \(h = 300\) mm water column and a flank ventilation scheme, the need for sectional ventilation arises when the dimensions of the mine field along the strike exceed 3000 m; and with a central ventilation scheme, when the dimensions of the mine field along the strike exceed 1500 m (Table 7).
References Used
- Komarov V. V. and Borisov D. F. — Mine Ventilation, 1938.
- Pokrovskii N. M. — Driving of Mine Workings, 1945.
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Maximum mine output according to Order No. 53 of the Ministry of the Coal Industry of the Eastern Regions of the USSR. ↩