- •Gold mining
- •Text 1. Some facts from the history of gold mining
- •Diamond Placer
- •Text 3. La paz placers
- •Text 2. Placer mining вy excavating machinery
- •Fig.1. Ruston-Bycyrus dragline excavator
- •Fig. 2. Dragline making first cut
- •Fig.5. General arrangement of property for dragline mining
- •Text 3. Power shovels
- •Cableways
- •Text 4. Excavating equipment in тнe mid 80s
- •Electric mining shovels
- •Hydraulic excavators
- •Fig. 13. Ransomes and Rapier w2000 walking dragline stripping overburden at phosphate mine in Jordan
- •Fig. 14. Shows the rh120c introduced in 1933 as an intermediate size between the rh75 and rh300, incorporating “Tripower" geometry
- •Text 2. Dredging in the north
- •Stripping
- •Dredging
- •Vocabulary
- •Text 3. Thawing
- •Other operating problems
- •Nodules
- •20° Angle Gave Best Results
- •Fig. 17. Nodule dredge configuration shown was chosen after a series of increasingly complex dredge designs
- •Larger Dredge Lines Cause Problems
- •Dredge Vessel Specifications
- •Ship Positioning By Dead Reckoning
- •10 Tpd Average
- •Fig. 18. Stages in mining diamondiferous gravel
- •Transport
- •Milling
- •Effects
- •What is Cyanide?
- •Prevention/Solution
- •Text 2. Sluicing
- •Sluice Boxes
- •Water Required
- •Tailings
- •Text 3. Excavation and treatment of gravel
- •Fig. 29. Sluicing by direct loading method
- •Fig. 30. Method of working with ample water supply and steep valley
- •Text.2 working of terrace and alluvial deposits
- •Fig. 33. Method of working river terrace and eluvial deposits
- •Fig. 34. Example of exploitation plan
- •Text 2. Hydraulic mining
- •Fig. 35. Sketch of giant or monitor
- •Text 3. Hydraulic elevators
- •Fig. 41. Hendy hydraulic gravel elevator
- •Fig. 42. Section of elevator pit (Joshua Hendy Iron Works)
- •Text 4. Sluice boxes for hydraulicking
- •Text 2. Miscellaneous methods of mining
- •Text 3. Khetri copper complex
- •Text 4. Kherti and kolihan mines
- •Fig. 46. Longituainal section of Kherti mine, showing principal shafts, main levels and stoping areas
- •In Kolihan mine, small footwall ore-shoots are worked by a sub-level top-slicing method using jackhammers and remote controlled Cavo loaders.
- •Shafts at the Kherti and Kolihan mines
- •Fig. 48. The service shaft, Khetri mine
- •Central services
- •Personnel and housing
Other operating problems
The weather is the prime factor making for uncertainty prying on the operations. There is, for instance, a wide difference between a severe winter with plenty of snow and one equally severe with little or no snow. In the latter case, the winter's frost will often penetrate seven or eight feet into thawed ground. A most important aspect of the winter weather is the temperature of the later month particularly March and April. A cold snap in April may have an altogether disproportionate effect in delaying operations. Much depends, too, on the amount of sunlight available in the spring months. A cloudy spring means the slower thawing out of the ground with lower water temperatures and delayed stripping and thawing.
As the winter comes on the water supply falls off, the frost becomes severe. As long as the dredge can keep moving, the dredge ponds can be kept open even in temperatures as severe as these but when, as often happens in the fall, the first severe freeze-up means a sudden drop in the water supply at the power plant with insufficient power at the compulsory stopping of several dredges, the dredge ponds may freeze so solidly that the smaller dredges cannot be restarted.
As the weather gets still colder and winter settles down, the principal problem, after that of power, is to ensure that the dredges are kept sufficiently warm to allow the material dug to be washed without freezing solid. The winter frost does not penetrate into the ground with sufficient rapidity to afford any serious obstacle to the dredges; in fact the month of October is often the best digging month of tin year. It is general drop in efficiency rather than any difficulty in digging, that is a determining factor even when there is sufficient power, in compelling the management to decide to close down the last operating dredges.
COMPREHENSION CHECK
Exercise 16. Complete the sentences with the missing words.
Since the material can not be washed away, it must be thawed in place and for that purpose water must be ... to its full depth.
Water is pumped through a series of ... 1/2 and 3/4 in.dia at a prevailing pressure of about 20 lb. per sq.in.
The water from a thawing point emerges at bedrock and ... around the bottom of the point and up through the ad joining gravel.
Much depends on the temperature of ..., the depth and nature of the gravel.
Water that has been used for stripping cannot be taken up in the run-off and used for thawing without ... the thawing points and the gravel itself.
Exercise 17. Look through text 3 and find the English equivalents to the word below. Use them to make sentences.
точка; оттаявший; просачиваться; недостаток воды; сток; засорение; расстояние между точкам; недостаточно оттаявшая залежь; износ оборудования; мерзлота; солнечные лучи.
Exercise 16. Answer the questions based on the information from the text.
What has to be done with the material which сan not be washed away because of frost?
What water is used for thawing?
How is water introduced into gravel?
How are points spaced? What is the standard of points?'
What factors does the speed of thawing depend upon?
What is a "sweater"?
What factors influence the period of thawing?
What are the problems of thawing in old working"?
Where is it possible to take water for thawing?
How does the nature of the gravel influence the process of thawing?
VOCABULARY
nodules - конкреции , валуны, друзы
viable - жизнеспособный
traction winch - тяговая лебедка
reel– барабан
a rack - разгрузочная рама, решетка
a bin - бункер
a van - грохот
a tow - бечева, буксир, трос
a wheel - колесо
haul - доставка, подвозка, волочить, тянуть
aft - на корме, по направлению к корме
tugger - вспомогательная подъемная лебедка, скреперная лебедка
shield - колпак, экран, предохранительный кожух
deployment - размещение
stern - корма
slack - слабина, ослабление натянутости
pivot - шарнир, цапфа
brace - распорка
pull - тяга, тянуть
hardware - корпус .металлическая часть, механизм
launch - запуск
stringer - прожилок
circumferential - круговой, периферийный
stiffener – загуститель, усилительная ленточка
rear - задняя часть
threshold - порог
torque - момент кручения
swivel joint - шарнирные соединения
gear – шестерня
socket - муфта, раструб
Exercise 18. Read the text below looking for the main ideas concerning dredge equipment and specification.