ANALYSIS OF THE WORK OF COAL MINERS IN LONGWALL FACES AT THE PROKOPYEVSK MINE OF THE KUZBASS

LEONOV P. A.
Candidate of Technical Sciences

Introduction

Work on studying the labor of coal miners in longwall faces under different mining systems was carried out by a brigade of the Tomsk Industrial Institute named after S. M. Kirov¹ in 1940 at the mines of the Prokopyevsk mine of the Kuzbass. At the mines of this mine, the most varied mining systems are used, which provided grounds, in selecting the objects of study, for choosing the indicated mine. In addition, it should be noted that limiting the area of work to one mine with recurring seams facilitated the conduct of a comparative analysis. In accordance with the assignment of the Kuznetsk Scientific-Research Coal Institute (KNIUI), the following mining systems were taken for studying the work of coal miners: long pillars along the strike with caving of the roof (DStO)², inclined slices with stowing (NSlZ), diagonal slices with stowing (DSlZ), systems with shield support and caving of the roof (ShchO), and horizontal slices with caving (GSlO). The method of extracting coal in the longwall operations at the objects of study was quite varied: by explosives (VV), by pneumatic hammers (OM), with the use of undercutting machines (VM), and by a combined method using pneumatic hammers and explosives (OM + VV).

Only such stoping workings—the workplaces of coal miners—were selected for observations and collection of materials as were in normal condition and in full development with respect to the work front. Of all the work in the longwall face, only coal work was investigated (coal extraction); repairs, roof-control work, preparation for stowing, and cutting operations were not examined, although in fact they were included within the range of the coal miners’ duties; we consider that the study of these works, in view of their considerable scope and complexity, should be carried out separately. The primary materials for studying the labor of coal miners were: 150 time observations of the 50 best coal miners and data from reports on the volume of work of these same workers over 10 days, as well as descriptions of workplaces obtained as a result of their examination in the mine. The processing of the materials obtained was carried out in the direction of analyzing the working-time balance, studying the elements of the principal operations, analyzing downtimes, making a comparative analysis of the productivity of coal miners, and identifying the particular features of the work of coal miners under different mining systems. In conclusion, conclusions are drawn

Table 2

Table 1

Conventional designations:

PZ — preparatory and concluding operations

VR — auxiliary work

OR — principal work

PR — extraneous work

Otd. — rest

Pr. — downtime

Instr. — production instruction

Shch2O — double shield

Shch3O — triple shield

Table 3

corresponding conclusions were drawn and specific proposals were developed for eliminating irregularities in the work and for increasing the productivity of coal-face workers.

Brief Description of the Workplaces and Results of Observations

The system of mining by long pillars with caving was used in seams of thin and medium thickness. In seams of medium thickness, the level was divided into sublevels with an inclined length of 20 m; in thin seams, the size of the extraction pillar along the raise was equal to the height of the level. The caving interval varied from 12 to 20 m. Under the system of mining by inclined slices with stowing, seams from 5 to 10 m thick were worked at a dip angle of up to 65°. Extraction of the slices proceeded from the bottom upward; dry stowing from native rock or from burned rock was used. Individual slices were 2.1 to 3.5 m thick; they were extracted by the system of long pillars along the strike. Under the system of mining by diagonal slices with stowing, only one seam was worked—the Internal IV—9 m thick. The inclination of the individual slices was set at 50°, their thickness at 2.5 m, and the length of the working face along the dip was 25 linear meters. The slices were extracted in ascending order. By horizontal slices with caving, a seam 5.2 m thick was mined. Shield support was used in the mining of thick seams by long pillars with extraction along the dip and with roof caving. Extraction was carried out through the full thickness of the seam for the entire level. The dip angle of the seams was from 62 to 90°; their thickness ranged from 7.3 to 14.5 m.

In thin seams, longwalls 40–50 m in length were used, with supports set every 1.4–1.5 linear meters; in seams of medium thickness and in individual inclined and diagonal slices there were also longwalls, but 20 to 25 linear meters long, with supports every 1.2 linear meters; shield systems had a working-face width along the strike of the seam from 17 to 25 linear meters, with support by a metal shield with a wooden cap piece. Coal extraction was carried out by blasting (with blastholes drilled by electric drills), by pneumatic picks alone, by a coal-cutting machine with a curved jib, and by one with a straight jib; in some seams, combined methods were used (a combination of cutting machines with explosives). The hardness of the coal in all the working faces we examined was established as category III (according to the Kuzbass norm-book). More detailed data on the seams, mines, and working faces where we studied the work of coal-face workers are given in Table 1.

During the period of our survey, two coal-face workers were employed in each working face of all mining systems. They performed drilling, breaking down coal, timbering with preparation of timber and lowering it from the ventilation drift to the place of support installation. When pneumatic picks were used, the coal-face workers mined coal with these mechanisms; when coal-cutting machines were used, after undercutting, the breaking down of the coal and the timbering were included among the duties of the coal-face workers. The latter assisted the shotfirer if blasting of the holes was carried out in the middle of the shift. It should be noted that sometimes coal-face workers performed the work of clearing coal from the face. In addition, at some mines the coal-face workers were assigned work on roof caving, repairs of the working face, and preparation of the working for erecting stowing in it. Thus, in the steep seams of the Prokopyevsk Mine, the work profile of the longwall coal-face worker is quite varied.

In processing the time observations (Table 1), in accordance with the existing profile of coal-face workers, the following classifications of work processes and operations were adopted.

1) Preparatory and concluding operations—preparing and putting away tools and the mechanism at the beginning and end of the shift, inspection of the face, installation of shelves (on steeply dipping seams) at the beginning of the shift.

2) Main work—drilling shot holes in the coal, breaking up coal after blasting, breaking with a hammer or pick, partial loading of coal (from the face), timbering (without cutting and lowering timber).

3) Auxiliary work—assistance to the shot-firer, preparation of the niche, cutting timber for up to 10 minutes per round (only for sawing or trimming one end of the props), lowering timber along the longwall itself (not more than 20 minutes), setting up knocked-out props, and other minor repairs.

4) Extraneous work—delivery and lowering of timber for more than 20 minutes, cutting timber for more than 10 minutes per round, going for tools, materials, or a shovel, and all other work connected with diversion from the processes indicated above in points 2 and 3.

5) Breaks—explicit rest, production briefing (conversation with the mining foreman, with one’s partner about the work), stoppages for various reasons.

Data on the balance of working-day time and productivity have been brought together in a summary table by systems (Table 2).

The best utilization of working time by two partner coal-face workers is obtained when one of them works as the assistant of the coal-face worker. Table 2 confirms this proposition very clearly.

The breakdown of the main work of coal-face workers in extraction faces into elements gives very interesting material on the profile of the coal-face worker. Corresponding tables were compiled for all systems. Below is given a brief summary from these tables (Table 3), from which one can obtain data on the ratio of time spent on drilling, breaking up, and timbering.

The main material from the analysis of the results of observations and the study of the work of coal-face workers is presented in the following conclusions.

Conclusions on the work of coal-face workers under various mining systems

A. Under the long-pillar system with caving, using undercutting machines and pneumatic picks

1. In machine longwalls, in the balance of the coal-face worker’s working time, the largest percentage falls on the main work (62–70%).

2. Downtime during coal extraction by undercutting machines, owing to the minimal use of BB, is insignificant; it amounts to 1–2% of the total time.

3. The making of the undercut, because of the specific nature of the work, in longwalls on steeply dipping seams is alternated every 10 m with drilling and breaking up. The absence of continuous operation of the machine along the whole length of the longwall leads to the necessity of assigning the machine operator to break coal.

4. When using an undercutting machine with a curved jib on seams similar to the “Pioneer” seam (with a thickness of 1.2 m and a dip angle of 65°), good results can be obtained. After the undercut, a large percentage of the undercut coal falls away, and the coal-face worker has only to do a small cleaning of the face (1.7 minutes per 1 m³ of coal).

5. The total working time of the coal-face worker in machine longwalls is 97%, and in pick longwalls it reaches 65.5%. These are the best indicators of all mining systems.

1. When only jackhammers are used, greater downtime for the face worker occurs during blasting of the blast holes and ventilation. Downtime amounts to only 3–4%.

2. In seams with stronger coals, with combined work by jackhammers and explosives, practice shows that the productivity of face workers increases, but, on the other hand, downtime increases to 10%.

3. A face worker using a jackhammer, while working in a development face, spends more than 50% of his main work on coal extraction; the expenditure of main work on timbering amounts to from 29.3% to 48.4%.

B. Under the long-pillar system with caving and with the use only of explosives for coal extraction

1. The work of a face worker under this system has the following specific features: a) a poor work rhythm (blast holes are fired one to three times per shift; the workers interrupt their work, often alternating breaking down, timbering, and drilling); b) during firing and ventilation, the face workers leave the longwall area and wait for 30–70 minutes. Part of this waiting is rest, part is pure downtime, but this rest is concentrated and compulsory, and often simply irrational; c) blasting operations sometimes entail disturbance of the timbering and blockage of coal chutes by large pieces of coal, which necessitates the face worker’s performance of auxiliary and extraneous work. In addition, it should be noted that, when blast holes are fired, the face worker, assisting the shot-firer in charging the blast holes, spends an additional 20–30 minutes of his working time.

2. The working-time balance of a face worker, on average for all faces (longwalls), gives a proportion of main work of 51% and downtime of 15%. These indicators are much lower than in machine and jackhammer longwalls.

3. The time spent by the face worker on the production of main work is distributed as follows: drilling 15%, breaking down coal 24%, and timbering 61%. Thus, the face worker spends two thirds of his main work on timbering and only one third on coal-extraction operations.

4. A face crew of workers consisting of two equally skilled face workers is not fully loaded with main work. Staffing the face crew with one qualified face worker and one worker of lower qualification will make it possible to use the labor of such senior face workers more rationally.

5. The productivity of face workers in longwalls reached, per shift, from 18 m³ (in a seam 1.4 m thick) to 38 m³ (with a seam thickness of 3.5 m). The maximum productivity was observed in longwalls and seams when the development face height was 3–3.5 m. The average productivity over all seams and longwalls was 28 m³ per face worker per shift.

V. Under the system of inclined slices with stowing

1. The working conditions in longwalls of an individual slice, when the rib is in good condition and stowing is supplied in a timely manner into the mined-out space, do not differ from those in longwalls under the long-pillar system in seams of medium thickness. This is confirmed by the almost identical structure of the working-time balance and by almost the same productivity indicators of the face workers under both mining systems.

2. The productivity of face workers in the first slice per shift, for example, in the Gorely seam, was 38 m³; in the second slice, 31 m³; in the third, 33 m³; and in the longwalls of the Vnutrennii I seam, 30 m³. Consequently, the indicators for the two

differ little from those under the longwall system for the first inclined seams.

1. Work in the third inclined seam (in the order of extraction) is less productive than in the first two; moreover, a study of the situation of the coal-cutter’s work in the first seams indicates the need to carry out extraction not everywhere with the use of explosives.

G. Under the system of horizontal seams with caving and diagonal seams with packing

1. In the balance of the coal-cutter’s working time on horizontal seams, auxiliary work occupies a large share (34.3%), consisting mainly of shoveling. This circumstance was one of the main reasons for the coal-cutter’s low productivity.

2. The balance of the coal-cutter’s working time in stopes under the system of diagonal seams gives a good structure with respect to the distribution of work and breaks (the latter amount to only 3.5%), but, despite this, productivity was recorded as low—12 m³ per shift.

3. The main reason for the low productivity in diagonal seams should be considered the unfavorable conditions for coal extraction: undercutting is carried out across the planes of bedding and cleavage; it is difficult to maintain an even roof of the working in the form of a plane directed at a definite angle to the horizontal plane; work near the ventilation drift is not entirely safe, etc.

4. For coal extraction in diagonal seams, the coal-cutter spends more than 70% of his main work and 30% on timbering. This ratio is the reverse of the figures in longwall faces and in inclined seams.

D. Systems with shield supports and roof caving

1. The balance of the coal-cutters’ working time is clearly unsatisfactory: time spent on main work is 21–53%; auxiliary work (mainly timbering and shoveling) takes up to 45% of the total working time; downtime due to blasting of boreholes and ventilation afterward amounts to 5–13%.

2. The productivity of the coal-cutter under shield systems was 29–37 m³ per shift (not counting dismantling and work preparatory to installation) and ranks first, competing with inclined seams (not counting packing work).

3. The organization of work has a number of shortcomings, as a result of which one of the coal-cutters in a pair working simultaneously is little occupied with his main work.

E. General conclusions on stope work for all the preceding mining systems

1. The total duration of the working day, on average for all systems, is 445 minutes, or 7 hr. 25 min.; the minimum was recorded on horizontal seams—424 minutes, the maximum—in the longwall faces of mines No. 3–3-bis and in the inclined seams at the Chernaya Gora adit—469 min.

2. In general, regarding the duration of the coal-cutters’ presence at work, it may be said that they make full use of the allotted time and even work somewhat beyond it. The Decree of the Presidium of the Supreme Soviet of 26/VI 1940 is being fulfilled by the leading workers.

1. Breaks in work consisted of time for rest, production instruction, and stoppages. The expenditure of time on explicit rest amounted to from 0.6% to 4.6%, and on average over all observations to 2–3%. The time of all actual rest was not established because it was impossible to record it by objective indications.

2. The minimum stoppage time was recorded in the system of diagonal seams—0.5%; the maximum in the faces of Internal I of mine No. 3-3 bis—17%; inclined seams over all beds gave 14.2%, shield systems—10.4%, and horizontal seams—only 2.8%.

3. The largest and most systematic stoppages of coal-face workers were observed during the blasting of shot holes in the middle of the shift. Quantitatively these stoppages took from 17 to 74 minutes of time, and on average over all systems about 1 hour.

Proposals

1. In faces under the long-pillar system on seams of medium thickness (from 15 to 37 m), in inclined seams, the two coal-face workers working simultaneously in a shift should be replaced by two workers, of whom one must be a qualified broad-profile coal-face worker, and the other less qualified, with the status of an assistant coal-face worker.

2. In stoping faces of horizontal seams, the same reorganization of the face crew should be made, and the worker assisting the coal-face worker should be assigned the shoveling of coal away from the face.

3. In stoping workings with shield support, the shift crew should be composed only of one coal-face worker and one or two assistants assigned to him, to whom the work of breaking down the coal, shoveling it away, and other auxiliary work should be entrusted. The coal-face worker himself should be assigned to drilling shot holes and only partly to breaking down coal and, in addition, should be entrusted with directing the work in the whole face. In critical places under the shield, the breaking down of coal must be done personally by the coal-face worker.

4. In machine faces, where after the kerf is cut little work remains for the coal-face worker in winning the coal, it is more expedient to have timbermen rather than coal-face workers for minor breaking down of coal and setting supports.

5. In all systems with immobile support of the stoping face, in order to relieve coal-face workers from extraneous work in cutting and lowering timber, the performance of the latter operations should be organized by special timber cutters and timber lowerers. For the complete freeing of coal-face workers from timber delivery, it is necessary to expand experiments, where conditions permit, in delivering timber to the very place where the support is to be installed not by coal-face workers, but with the use of small-scale mechanization.

6. In order to rationalize the very labor-intensive process of support work in the stoping faces themselves, on steep seams it is necessary to accelerate the mechanization of lowering timber into the face and of the work of installing chocks. In this respect, at the present time the earliest implementation of the proposal by engineer V. F. Parusimov on the mechanization of work for supporting faces on steeply dipping seams is of great interest.

7. In hammer faces, in order to eliminate pick work, which is less productive, and to increase the productivity of the breaking hammer by creating a more convenient position for it (not suspended, below the waist, and not with outstretched arms), the face should be arranged benchwise and the belt in the face should be worked from top to bottom.

8. To eliminate stoppages caused by blasting shot holes and ventilating the face, radical technical and organizational measures must be adopted. These stoppages are observed under all systems of mining where explosives are used. The main measures are

may be: (a) moving blasting from the middle of the shift to the interval between shifts; (b) improving ventilation by installing additional fans or increasing the supply of air in the main current during blasting operations.

1. In order to reduce idle time due to a shortage of tools, their poor quality, and untimely delivery of materials, organizational measures must be taken specifically for each development face.

2. In view of the absence, in the list of miners’ occupations, of the qualification of assistant face worker, it is advisable now to work out, in the appropriate organizations, the question of formalizing this new, but in fact already existing, qualification, or of differentiating face workers into two grades, analogous to foremen and carpenters.

1. The brigade was organized by the Department of Mining of Coal (Stratified) Deposits under the direct supervision of the author of the article and with the participation of students. ↩

2. In parentheses are indicated the conventional designations adopted by the author for the mining systems and the place of coal extraction. ↩