- •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
Text 2. Dredging in the north
There have been three main reasons for the development of the dredging industry during recent years and the increased prosperity now being experienced in the North. These are:
The development of a method of thawing frozen gravel by cold water instead of steam, with a resulting saving in cost of from 25 to 40 per cu.yd.
The development of a successful method of "stripping” or flushing off the thick layer of barren frozen "muck" or tundra which overlies the gold-bearing gravels so that it is now no longer necessary to dredge this "muck" in place.
The increased price of gold. The ground is studied in cross-section for depths, both of muck and gravel, and calculations are made of the amount of muck, the amount of gravel, the volume of “dredging section" (gravel plus bedrock containing payable values) and, finally gold content. This last is determined by calculation on a triangular basis, the values attributed to each triangle being a weighted average of those found from the drill holes at its apices.
At the same time, the dredge limits of payable values must be determined and the width and course of the dredge path decided upon.
Stripping
When the ground has been surveyed, and the dredging area determined, the company has to make provision for roads, electric power lines and camp buildings. Next, in order of sequence, comes the assembling of stripping equipment and the commencement of stripping operations.
The creek gravels are almost invariably frozen to bedrock, except beneath the running water of the creek itself (the so-called "naturally" thawed ground). Hill and bench gravels are also frozen except in very deep ground where the frost does not seem to be able to penetrate. The perpetually frozen condition of the creek gravels is maintained throughout the summer by the protection afforded by a layer of frozen silt called “suck”. This material consists mainly of decomposed vegetable matter and fine silt and a large proportion (50 %) is water. On top of this frozen muck there is a growth of moss and grass; bushes and small trees also grow. The depth of muck varies on the different creeks, but is rarely less than ten feet and is sometimes thirty. It contains no values. The difference between the underlying gravel and the overlying muck is primarily that the latter can be washed "stripped", or flushed off, down the natural drainage channels of the streams. The gravel cannot be carried away by water and must be thawed “in situ”.
Stripping, or the removal of the muck, is effected by the use of water under pressure in very much the same way as in the case of hydraulic mining. The given area is carefully surveyed with particular attention to the underlying grades on top of the gravel so that there may be at all times a good run-off for the material stripped. When the first drains have been cut to serve as run-offs, a row of hydraulic "giants" is set up, spaced at regular intervals and these nozzles are allowed to play, in succession, upon the surface of the muck. A certain depth of surface has already been thawed by the sun’s rays and operations with each "giant" are continued to the point where such sun-thawed material has been washed away and the underlying ice exposed. As soon as this stage has been reached, the operator shifts his ground to the next "giant" some 100 ft. or more away and commenced again to play on the surface with this nozzle until the same stage has been reached and frost again exposed. In this way, in succession, each nozzle is operated until the end of the line is reached by which time the sun will again have thawed a certain depth around the nozzle at the head of the line where operations can again be resumed.