Fig. 35. Sketch of giant or monitor

a complete circle to any position desired in a horizontal plans about the joint A and can be deflected vertically through a rage of about 60⁰ (50⁰ above and 10⁰ below horizontal) about the joint B. The nozzle C, through which the water issues, is fitted with guide vanes, which prevent a scattering or rotary motion of the jet, as it is discharged, and ensure that the water is forced out in a straight and direct line and in a solid unbroken colum. Water entering the giant exerts a strong upward pressure the thrust of which is taken by the kingbolt D.; and a weghted lever E, controls the horizontal and vertical movements and also counterbalances the weight of the giant, which is bolted to a heavy baulk of timber or to a frame of timbers by the bracket or plate F. The timber, in turn, should be well weighted down or else bolted to bedrock.

Small giants and those working under a low head are directed by hand and are usually not fitted with deflectors, but where the head exceeds 100 feet deflectors should be employed; these consist of a ball-and-socket coupling, inserted between the nozzle and then spout of the giant, and controlled by a lever, which enables the giant to be pointed in any direction (fig. 36, 37).

Fig. 36. Hendy hydraukic giant

Fig. 37. Types of deflectors for giants

Fig. 38. Hydraulicking the White Channel deposits near Dawson City. Yukon territory, with Hendly giants

In mining operation with a giant, work should generally be commenced at the lowest part of bedrock, and the giants placed at a distance of from 50 to 150 feet from the base of the banks, depending on the depth of the latter and the methods of operation. Great care must be exercised, if the giants are worked close up to the foot of the banks, that a cave does not occur, which might bury both giants and workers.

It is bad practice to work into a bank with a "horse-shoe" cut, as by this means the giant becomes surrounded on all s des with high banks, thus greatly increasing the danger of operations. The best plan is to work right across the face of the river channel, with a tendency to maintain a "nose" of gravel immediately in front of the giants and to work with a side cutting action both left and right of this nose, as by this means the direction of slides would be parallel to the main face of operations, and not toward the giant.

A small-sixed nozzle should be used for under-cutting, and it will generally be found that a side-cutting action will excavate a far larger quantity of gravel per cubic foot of water used than by "pounding" the column dead on the banks.

There is no rule for the actual location of the giant. This will depend entirely upon the conditions existing at the mine, and will vary from time to time as the work is carried forward. The actual setting of the giants, however, is a matter of considerable importance, and they must be carefully and securely braced or accidents are likely to occur which may cause serious trouble and delay. In many ca­ses an expansion joint is used to make the final connection between the end of the pipe-line and the base of the giant. If the pipe-line has been put together with lugs and wired joints, and is securely anchored at the foot of the grade and at various important points, this will be found to bе a good practice, as the giant is then free from the creeping action of the pipe due to expansion and contraction, and the only factor to be considered is the pressure of the water.

If there is a slight upward trend in pipe-line there will be an upward lifting action on the giant, which will make it extremely difficult to hold it down firmly in place. If the last few lengths of pipe-line are carried on some slightly raised portion of bedrock, or on logs, so that at the final and terminal connection the direction of the pressure of the water and of the pipe-line will have a slight downward inclination, there will be far fewer chances that the foundation of the giant will move (fig. 39, 46).

The foundation piece should be a heavy square timber, in size proportionate to the number of the giant and from. 8 to 10 feet long, laid in a trench excavated in bedrock.

Fig. 39. Booster giant

Fig. 40. Booster giant in section

The giant should be bolted to this timber, carefully located to the face of the timber and the face of the base of the giant on a line directly at right angles to the thrust of the water and the terminal lengths of the pipe.

The success of all hydraulic mining work will depend largely upon the proper construction of the sluice boxes and their grade and location, as it is very essential that the gravel shall be removed as fast as it is mined by the giants, also that it shall be properly washed and disintegrated, so that the mineral is freed from the lumps of adhering gravel, and that the clay shall be thoroughly washed, to avoid any possibility of the mineral contents being carried away by large lumps of mingled clay and stone travelling down the sluices.

When only one giant is in operation, it is first employed to excavate the gravel and then to wash the disintegrated material through the bedrock ditches to the sluices, but if two giants are in operation, one is usually employed on excavation work while the other is used for washing the broken down material to the sluices. The number of giants used will depend entirely on the size of the deposit, the quantity of water available, and the head obtainable, but it is good practice to use a small number of large giants than a large number of small giants, as the former excavate more gravel.

The excavated material together with the water is carried away from the working faces to the sluices by means of drains or ditches cut in the bedrock, known as bedrock cuts, and should have at least a 4 to 5% grade. Should the grade be insufficient, the movement of the material may be accelerated by the employment of a "booster giant". This giant has no horizontal movement hut the vertical range is sufficient to permit the direction of a stream of water with sufficient pressure to keep large boulders moving and to keep the gravel mined by the giants travelling towards the sluices. The booster giant is also employed to facilitate the movement of material in sluices having insufficient grade.

Where deep gravels are to be opened up by means of a bedrock tunnel, it is customary to give this tunnel a grade of from 4 to 5%t and it is generally best to bottom the gravel deposit with a deep shaft before commencing to drive the tunnel, so as to be able to carry the necessary surveys over the intervening ridge and thereby locate the proper level at which to commence the mouth of the tunnel, due allowance being made for grade and distance, to avoid all danger of the tunnel being driven at too high an elevation and coming out in the gravel above the bedrock, Under the above conditions of , mining deep gravels, where natural drainage can be obtained by means of a tunnel, it is very often a serious problem how to commence the actual washing of the banks, as it commonly happens that there is no section of bedrock conveniently exposed which will communicate with the tunnel and where mining operations may he begun.

The tunnel is usually driven a little to one side of the main vertical shaft and a short cross-cut is made to connect the bottom оf the shaft with the tunnel. The base оf the tunnel is then heavily and securely timbered, and, if the bedrock is soft, a pit is excavated and floored with timber, and filled up to the tunnel level with boulders of hard stone or quarts. The shaft is then lined from top to bottom with heavy planking placed inside of the frame timbers, so as to protect them from wear and displacement. If the tunnel is located in rock sufficiently hard to resist erosion, this is used as a natural race otherwise the tunnel is securely timbered and the flume is built inside and communicates with the bottom of the shaft.

Mining operations may now be commenced at the mouth of the shaft, and the frame timbers and lining may be removed step by step from the surface downwards, as benches of gravel can be conveniently worked back from the mouth. The gravel as it is broken is piped directly into the shaft radius all around the shaft, another set of timbers may be removed and a second bench commenced. It is not advisable to attempt to crowd this preliminary work or to strip too many timbers and commence too deep a bench at one operation as a "jam" is likely to occur in the neck of the shaft, which would be found costly and difficult to remove. Operations have been successfully carried on as outlined, through vertical shafts having a depth as great as 200ft. Attempts have been made to drive inclined upraises from the end.

Duty of giants. The duty of giants varies considerably with local conditions, such as the height of the gravel banks, the nature of the gravel and bedrock, head of water obtainable size of jet, etc. It is usually stated to be 1,5 cubic yards of gravel per 24 hours for every cubic ft of water per minute used, or in other words, 1 cubic ft of water per minute will treat 1,5 cubic yard of gravel in 24 hours.

COMPREHENSION CHECK

Exercise 8. Complete the sentences using the information from text 2:

1. The cheapest form of gold mining is ...

2. Hydraulic mining or hydraulics consists...

3. Giants, or monitors as they are generally called, are employed for...

4. Great care must be exercised when ...

5. No rule can be given for the actual location of the giant. This depends entirely on ...

Exercise 9. Find the English equivalents of the words and word combinations in the text:

Самый дешевый способ золотодобычи, значительные запасы золотоносного песка, устойчивый отвал, правильного установленные шлюзы, отбойка и перемещение наносов песка, ударная сила воды под давлением, верхний слой наносов, почвенно-растительный слой, мелкий песок с небольшим содержанием золота, гидромониторы, разработка торфов, выгонка песка из забоя, управлять вручную.

SPEAKING

Exercise 10. Answer the questions, discuss them with the partner.

1. What is hydraulic mining?

2. Where can this method be employed?

3. What are the necessary conditions for using this method?

4. Have you ever seen the operation of giants?

5. What prevents a scattering or rotary motion of the jet?

6. Where are the giants placed?

7. Can any rule be given for the actual location оf the giant?

8. When only one giant is in operation, for what purpose is it employed first and then?

LANGUAGE REVIEW

Exercise 11. Choose the form of the word (adverb or adjective):

1. Two people were ________injured in the accident. (serious/seriously)

2. He was ________ upset about losing his job. (terrible/terribly)

3. There was a ________ change in the weather. (sudden/suddenly)

4. The worker fell and hurt himself quite _______ . (bad/badly)

5. Platinum, like titanium, it is not _______ distributed. (wide/ widely)

Exercise 12. Write the common abbreviations and symbols in words:

1. 2^nd __second_____

2. + ____________

3. = ____________

4. % ____________

5. 100^oC _________

6. ½ ____________

7. Fig.2 ___________

8. i.e. ____________

9. e.g. ____________

10. 19,8 m³ ________

11. 400 ft __________

12. 200 t ___________

13. & ______________

14. 3/4 in ___________

15. 1,1 lb per ft ______

16. 4:1 _____________

17. 2 ½ ____________

18. etc _____________

19. 10,000 t/y________

20. 5,5 m dia ________

VOCABULARY

elevators - элеваторы

flat – плоский, ровный

suitable – годный, подходящий

favorable - благоприятный

utilize - применить

velocity - скорость

elevate - поднимать

upraise - подъем

upcast - восходящий

suction head – высота всасывания насоса

prevent - предотвращать

bar - колосник

grizzly – грохот, колосниковый грохот

throat - проход

efficiency - продуктивность

reinforce - укреплять

wear – износ

liner - прокладка, облицовка

Exercise 13. Find the meaning of the phrases below, try to remember them:

the nozzle water; natural water head; maximum lift height; hydraulic gravel elevators; approximate sluices sizes; hydraulic gold mining; dumping room; ascending water velocity.

READING

Exercise 14. Read the text below looking for the main ideas concerning hydraulic elevators.