DETERMINATION OF THE OPTIMAL LONGWALL LENGTH FOR THE “DONBASS” SHEARER UNDER INTEGRATED LABOR ORGANIZATION AT THE MINES OF THE “LENINUGOL” TRUST

I. P. GUSEV

(Presented by the scientific seminar of the departments of bedded-deposit mining, ore-deposit mining, mine construction, safety engineering, and mine ventilation)

The Party and the Government of the Soviet Union devote enormous attention to equipping the coal industry with new, more advanced machinery. In the postwar years, the coal mines have introduced the “Donbass,” “Gornyak,” UKT, UKMG, KKP, and other shearers. The introduction of shearers has made it possible to mechanize the most labor-intensive processes of coal extraction—the cutting and loading of coal in longwalls. At present, about 1,240 coal shearers are operating in the mines of the Soviet Union, along with a considerable number of undercutting, loading, and other machines; however, the use of this abundant mining equipment is often unsatisfactory.

At the July Plenum of the Central Committee of the CPSU (1955), a well-deserved reproach was made to workers in the coal industry that, despite the high saturation of mines with mining equipment, labor productivity is growing extremely slowly and remains very low. The reason for this is the poor utilization of the available mining equipment and the almost complete absence of mechanization of auxiliary work, the volume of which at some mines reaches 50 percent or more of the total volume of work.

For fuller utilization of the “Donbass” shearer, a clear organization of a whole series of production processes in the mine is necessary and, above all, the creation of a sufficient front of work and optimal conditions under which the shearer will be used more fully and productively. Full utilization of the shearer will make it possible to increase coal output and improve the technical-and-economic indices for the longwall. One of the basic conditions affecting the normal and productive operation of the “Donbass” shearer is the length of the longwall. Experience with the operation of such shearers in the mines of the Donets Basin shows that the best indices are obtained in those combines in which shearers operate in longer longwalls [6, 1].

At the mines of the “Leninugol” trust of the “Kuzbassugol” combine, “Donbass” shearers operate in longwalls of the most varied lengths—from 60–70 m to 200–210 m. Changes in the technical-and-economic indices of shearer longwalls, depending on their length, for 1954 are given in Table 1. The results of the operation of these longwalls are far from identical, although

in mining-engineering conditions there is no sharp difference. All the longwalls considered worked seams with a dip angle of 6–8°; roof control in the longwalls was by complete caving onto metal chocks, with a caving interval of 1–2 strips 1.45–1.60 m wide; coal haulage along the longwalls was by SKR-11 scraper conveyors; face support was wooden; the coals were of medium hardness; systems of longwall mining on the strike are used mainly, and partly on the rise; the organization of labor in the longwalls is integrated.

Analysis of the data presented in Table 1 shows that the highest productivity of the shearers was achieved in longwalls 130–150–180 m long. Theoretical studies also confirm that in longwalls of greater length the shearers can work productively for a significant part of the time (provided avoidable downtime is absent) and, consequently, coal output in such longwalls should be higher. The amount of time required, according to calculation, for coal extraction, dismantling, lowering, and installation of the shearer, referred to one and the same coal output in longwalls of different lengths (Table 2, Fig. 1), shows that a decrease in longwall length leads to an increase in time spent on nonproductive operations (dismantling and installation of the shearer); and, conversely, the longer the longwall, the smaller these expenditures. Thus, increasing the length of the longwall leads to a reduction in nonproductive expenditures and to an increase in the time the shearer works on coal extraction. However, an unlimited increase in the longwall is not advisable, since other factors appear that exert a negative influence on the normal operation of the longwall (roof control, coal transport, delivery of support and other materials into the longwall, movement of people along the longwall, etc.). Consequently, it is possible to find such an optimal longwall length for the “Donbass” shearer at which higher indicators of its operation are ensured.

Fig. 1. Time expended by the shearer in the longwall
(In the figure: vertical axis \(t_{\text{hr}}\); horizontal axis \(l_m\); curves: “shearer operating time”; “shearer preparation time.”)

It is recommended that the optimal longwall length be selected on the basis of the condition that one cycle per day must be carried out in this longwall. Under this condition, the work front is used more effectively, the mechanisms in the longwall are more fully loaded, a definite rhythm is maintained in the alternation of coal-extraction work and longwall preparation, and the organization of labor in the longwall is simplified.

Thus, the optimal longwall length for the “Donbass” shearer is determined by us from conditions under which the following are observed:

1) safety of work in the longwall;
2) maximum loading of shearers and conveyors;
3) higher productivity of face workers and the obligatory performance in the longwall of at least one cycle per day;
4) integrated crews work in the longwall;
5) the longwall is served by one shearer;
6) avoidable time losses are absent.

The formula for determining the optimal longwall length was pro-

Table 1

Technical-and-economic indicators

Table 2

Time expenditures for coal extraction and preparation of the shearer as a function of longwall length

many have been proposed. A considerable portion of them have not found practical application and at present are of only historical interest. Recently, for determining the optimal length of a shearer longwall, formulas have been proposed by Kucherov [3, 95], Sochinskii [7, 8], Rosentreter [4, 18], Martynenko, Entel [8, 122], and others.

The formulas of the authors indicated make it possible to determine the length of a longwall under a cyclic organization of labor, when there is a strict division between shifts into production and repair-preparatory ones.

The application of the new form of labor organization has changed the distribution of production processes over time. Under an integrated organization of labor, shifts are not divided into production and preparatory shifts. In addition, in this case fewer shifts are spent on preparing the longwall for stoping, which is not taken into account in the existing formulas. Therefore, using them under an integrated organization of labor gives understated results.

In this connection it is proposed to introduce changes into Associate Professor Kucherov’s formula and to present it in the following form:

\[ L_l = \frac{n\left(T_{sm}-T_{pz}\right)-T_{dm}-T_m} {\dfrac{1}{V_n}+\dfrac{t}{l_k}+\dfrac{1}{V_m}+\dfrac{t'}{l_k}+t_p+t_0} +l_n, \tag{1} \]

where \(L_l\) is the length of the shearer longwall, m;

\(n\) is the number of work shifts per day;

\(T_{sm}\) is the duration of one shift, min;

\(T_{pz}\) is the duration of preparatory-final operations per shift, min;

\(T_{dm}\) is the duration of dismantling the shearer, min;

\(T_m\) is the duration of assembling the shearer, min;

\(V\) is the working speed of the shearer, m/min;

\(t\) is the time for resetting the prop, min;

\(l_k\) is the length of the cable wound onto the shearer drum, 25--30 m;

$V_m$ — maneuvering speed of the combine during the downward run — 14.5 m/min;

$t'$ — time for resetting the prop during the combine’s downward run, min;

$t_p$ — time for other stoppages of the combine, min per 1 linear m of longwall;

$t_0$ — time for stoppages of the combine due to blasting operations, min per 1 linear m of longwall;

$l_n$ — length of niches — 8–10 m.

To determine the initial data entering into the formula, we carried out time observations and processed time-study records of the operation of combine longwalls at the mines of the Leninugol trust, totaling more than 1000 hours. On the basis of an analysis of the time-study records and time observations of the operation of combine longwalls, the following numerical values may be recommended for approximate calculations by the formula given:

$T_{sm}$ — 480 min; $T_{pz}$ — 40 min; $T_{dm}$ — 50–65 min; $T_m$ — 100–110 min, with larger values for thin seams and smaller values for medium seams;

$V_p$ — 0.2–0.5 m/min; $t$ — 7–8 min; $t'$ — 10 min; $t_p$ — 0.7–0.8 min/m; $t_0$ — 0.3–0.4 min/m.

Changing the picks is carried out during installation and stoppages of the combine for various reasons; therefore this time is not included as a separate term in the formula.

The results of determining the length of combine longwalls by formula (1) at different combine feed speeds are given in Table 3.

Table 3

Under the conditions of the mines of the Leninsk-Kuznetsk district, combines operate on average at a speed of 0.2–0.4 m/min; consequently, on the basis of combine productivity, the longwall length may be 210–240 m.

Time-study observations also show that, on average, in one hour of operation the combine advances 10–14 m; with integrated labor organization, coal extraction is carried out 18–20 hours per day. Thus, in longwalls 210–240 m long, with integrated labor organization, it is quite possible to carry out one cycle within a day.

We shall check the length of a combine longwall in terms of the productivity of delivery mechanisms, proceeding from the condition of the hourly productivity of conveyors and the combine, using B. A. Rosentreter’s formula [5,21]:

\[ L_d=\frac{t_d Q_{\ch}\varphi}{r m \gamma}, \tag{2} \]

where $L_d$ — longwall length according to delivery, m;

$t_d$ — duration of coal delivery in the longwall per day, 18–20 hours;

$Q_{\ch}$ — hourly productivity of the conveyor, t;

$r$ — cutting depth, m;

$m$ — seam thickness, m;

$\gamma$ — volumetric weight of coal, t/m³;

$\varphi$ — coefficient taking into account conveyor stoppages due to shunting with mine cars under the chutes.

The possible length of a shearer longwall in terms of the productivity of the delivery mechanisms, calculated by formula (2) for \(t_d = 18\) hours, \(Q_r = 60\) t/hour, \(r = 1.5\) m, \(\gamma = 1.3\) t/m\(^3\), is shown in Table 4 for seams of different thickness.

Table 4

It is evident from Table 4 that, in terms of the productivity of the delivery mechanisms, the length of a shearer longwall may be more than 200 m.

Under ventilation conditions, the permissible length of a shearer longwall may be determined by the formula [2, 21]

\[ L_v = \frac{60 V b \varphi m_0}{n r q_m C \gamma m_n}, \tag{3} \]

where \(L_v\) is the longwall length according to ventilation conditions, m;
\(V\) is the maximum velocity of motion of the air current in the longwall, permissible under safety regulations, m/sec;
\(b\) is the minimum width of the working space, m;
\(\varphi\) is the coefficient of narrowing of the longwall, caused by the reduction of the cross section of the working space as a result of the presence in it of supports and equipment—0.95;
\(n\) is the number of cycles per day;
\(r\) is the cutting depth, m;
\(q_m\) is the air requirement per ton of daily output, m\(^3\)/min;
\(m_0\) is the total seam thickness, m;
\(m_n\) is the useful seam thickness, m;
\(\gamma\) is the volumetric weight of coal, t/m\(^3\);
\(C\) is the seam extraction coefficient—0.95.

The length of a shearer longwall according to ventilation conditions, determined for \(b = 2\) m, \(\varphi = 0.95\), \(n = 1\), \(r = 1.5\) m, for seams of categories I, II, and III with respect to methane gas, is given in Table 5.

Table 5

Under ventilation conditions, the minimum length of a shearer longwall may be 200 m. Roof control in longwalls of such length will not have a negative effect.

In work [9, 294], V. D. Slesarev, considering the question of longwall length, states: “Analysis of this question has shown that an increase in the length of the face in itself does not cause deterioration of the condition of the roof and an increase in rock pressure, provided that the increase in the face length is not accompanied by a reduction in the rate of advance, the rate of performance of operations for controlling rock pressure.” And further, “...considering the question of longwall lengths, it is necessary to come to the conclusion,

Table 6

that at the present time the full possibility of controlling rock pressure in longwalls of “unlimited length” has practically been demonstrated.

At the mines of the Leninugol trust, longwalls 190–200 m in length were used in the Nadbaikaim, Baikaim, Emelyanov, Insk II, Boldyrev, and Tolmachev seams. Work in longwalls of this length proceeded normally; there were no cases of caving, and the accident rate did not increase. The labor input of roof-control work likewise did not increase with the increase in longwall length (Table 6)\(^1\).

Thus, the calculation carried out shows that the optimal length of shearer longwalls, with integrated labor organization, for the mines of the Leninugol trust is 200–210 m.

Therefore, there are no grounds for conducting extraction work at the mines of the Leninugol trust with shorter longwalls.

REFERENCES

1. Samoilyuk N. D. On types of scraper conveyors for coal mines. Ugol’ No. 5, 1950.

2. Ksenofontova A. I. Collection of Problems in Mine Ventilation. Ugletekhizdat, 1954.

3. Goikhman G. I., Lipkovich S. M. Problem Book on the Development of Bedded Coal Deposits. Ugletekhizdat, 1950.

4. Rozentreter B. A. Determination of the length of a longwall and the dimensions of the extraction field in mechanized development of seams in the Donbass. Ugol’ No. 5, 1954.

5. Miner’s Day. Ugol’ No. 8, 1955.

6. Sosnov G. A., Prudkin Ya. M. On the operating efficiency of shearer longwalls. Ugol’ No. 10, 1950.

7. DonUGI. Increasing the productivity of the “Donbass” shearer. Collection II. Ugletekhizdat, 1952.

8. Martynenko A. T., Entel A. V. Method for determining the optimal longwall length and the number of cycles per day. Problems in the Development of Thick Seams of the Kuzbass. Ugletekhizdat, 1953.

9. Slesarev V. D. Control of Rock Pressure in the Development of Coal Seams of the Donets Basin. Ugletekhizdat, 1952.

\(^1\) The calculation was made for a seam with a thickness of 1.3 m (author).