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Advantage disadvantage advantageous

1. As is known, the ... of long continuous faces is that they per
mit an almost 100 per cent of recovery of mineral.

2. Hydraulic mining is practised extensively at a number of col
lieries. It is one of the ... methods of mining.

3. As for the room-and-pillar method one must say that this
method of mining is seldom practised in Russia because it has some
...s.

4. One of these ...s is that the pillars between the rooms are
partly extracted.

30. per (, )
instead (of)
(, )'.

; ; ; ; -


206______________________________________________ Unit 8

31. ,
to be to have:

1. The various methods of mining involve production faces
which are either long (longwall) or short (shortwall) or room-
and-pillar.

2. Until mining machines were developed, short faces predomi
nated.

 

3. The aim was to reduce the volume of development work by
using the longwall method.

4. Some disadvantages of shortwall work are a considerable loss
of mineral which may reach and exceed 40 per cent, and the dif
ficulty of ventilation.

5. In gassy mines each face with its development workings has
to be ventilated with its own air current.

6. Cutter-loaders are being widely applied underground now
because these machines are the most progressive means for mecha
nising coal winning.

7. It is necessary to study all the factors which influence the
choice of the mining method.

8. There are special methods of extracting seams which are
close together ().

9. The shield method of mining has to be introduced in thick
seams, dipping at an angle of not less than 55-60", with regular
occurrence and hard coal.

10. They have to introduce new mining equipment as soon as possible.

32. ,
:

1. As the longwall method permits an almost 100 per cent re
covery of coal, all the seam is extracted and there is no coal left in
the form of pillars, except the shaft pillar.

2. No fissures were found.

3. We do not use the room-and-pillar method on a wide scale
because it is characterized by high losses of coal.

 

4. Nothing was said about special ways of extracting thick
seams.

5. In manless faces no men operate the machines, you can see
nobody in such faces as all the processes are fully automated.

6. A level is a horizontal road with no direct access to the sur
face.


Units_________________________________________ 207

33.
, :

Od the contrary; to my mind; In my opinion; as far as I know; as Is known; I'd like to stress that; I'd like to say that; let us consider

1. We say that the method of mining is rational if it guarantees
only safety of the men and maximum output of mineral.

2. It is rather difficult to define which method of mining
(longwall or shortwall) is more often used in Russia.

3. The shield method of mining is used where short faces are
worked. It is used in all the coal-fields of Russia.

4. The problem of extracting thick seams is not difficult. As a
rule, such seams are not extracted to full thickness.

5. In applying hydraulic mining powerful cutter-loaders win
coal and transport it to the surface.

34. .
:

1. What does the method of mining mineral deposits under
ground involve?

2. What main requirements should mining methods satisfy?

3. What types of production faces do the methods of mining in
clude?

4. What can you say about their application in different coal-
producing countries?

5. What methods of mining are practised in the Kuznetsk coal
field?

35. ,
:

1. The Location of the Mine, Its Geological Conditions (folds,
faults, disturbances, depth, seams, thick, sloping, steep, inclined).
Try to
explain why underground mining is used there.

2. The Type of the Deposit (tabular, bedded, vein).

3. The Method of Mining (longwall, room-and-pillar).

4. Mine Workings, Their Functions (vertical, horizontal, in
clined).

5. Average Output (annual, daily).


208 UnltS

36. ,
.

37. ,
.

:

goaf ;

double-ended drum bearer

Mining Thick Seams

Longwall retreating is one of the primary methods of mining in many coal mining areas. There is a high degree of mechanization, and mine safety is receiving an increasing amount of emphasis.

Thick seam coal mining is important in Russia. Many high-quality coal seams exceed 35 metres (12 feet) in thickness the normally accepted classification for a thick seam (although this varies in different countries). Some of these thick seams are of key importance in major mining basins. Seam thickness is the most significant factor which is taken into account in mining practice. The increasing strata movement with increasing seam thickness requires not only specialized extraction techniques, but also highly specialized ground control and support methods. This is certainly true of the coal basins where coal seams are gassy and the majority of coal is liable to spontaneous combustion. Coal seams occur at a depth of between 350 and 710 metres (1,150 and 2,330 feet).

Longwall retreating is the primary method of mining at the collieries with more than 98 per cent of the total output. Application of a mining method with the coal face being advanced down the dip is steadily expanding; shortwall pillar extraction with power loaders is being successfully employed.

Coal faces and development headings are equipped with instruments for automatic gas protection and centralized telemonitoring of methane content. Data on gas conditions in development headings which are particularly dangerous from the viewpoint of methane content, and in all coal faces are transmitted to the mine dispatcher's control panel. In order to reduce gas content in mine workings, extensive use is made of preliminary gas drainage of the coal seams, gas drainage of roofs to be caved and also of the goaf.


UnitS_____________________________________________ 209

The main trend in mine transport is towards high-capacity automatic conveyer systems. In underground workings transport of men and materials is by high-capacity electric locomotives; in incline roadways, by ropeways, floor-mounted haulage and up-to-date hoisting installations.

The mining district is usually developed by mine shafts. The mining method is longwall retreating along the strike and down the dip. The mining area is divided into two blocks east and west. In the eastern block, the panels are mined down the dip, in the western block, mining takes place along the strike. The faces are 200 metres long and operate along the strike of the seam. Sandstone forms the immediate roof and floor of the seam. Each face is mining a 3.5-metre thick section of coal, and a 0.5 to 0.8 metre thick pillar (band) of coal is left between two panels to form the roof of the lower face.

Each face is equipped with a double-ended dram shearer. The drams are 1.8 metres in diameter and a 0.6-metre web of coal. The leading dram cuts the top section of the face, and the trailing dram cuts the bottom section. Water jets are fitted to the drams for dust suppression. Coal passes along the face on the armoured face conveyer to the crasher installed at the main gate end of the conveyer, which reduces the size of the coal before it is delivered to a beam stage loader in the main gate.

The faces are operated on two production shifts and one maintenance shift per day.

Each face is supported by shield supports.

It should be stressed that special attention is paid to underground methane drainage. The methane is pumped through pipes first to the tail gate and then through the mine gate to the upcast shafts and then to the surface, where it is used for heating. Two sensors for continuously monitoring the emission of CH4 are situated in the top panel, one in the main gate, and the other in the tail gate. These are placed 20 metres in front of the face. The control room at the mine's surface automatically monitors and records CH4 emissions throughout the mine.

In coal face and development operations, use is made of current forecasting of the liability to sudden outbursts, that is establishing dangerous and non-dangerous zones.

All coal faces are equipped with mechanized complexes, comprising power loaders. In underground haulage roadways, use is made of high-capacity belt and apron conveyers. Coal is hoisted to the surface through two skip shafts. Monorails are widely used on levels for transport of materials and equipment to coal faces and



Unit 8


 


development headings. Some of production processes are automatic.

38. ) .
.

6) . .

39. :

1. Thick seam mining and problems connected with their re
covery.

2. Mechanization used in mining thick seams.

3. Underground methane drainage problems.

DISCUSSION

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lender

feasibility

In situ mining

screening ;

processing ,


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