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Waste removal of 100million/t of overburden,

Waste removal of 100million/t of overburden,

Waste removal of 100million/t of overburden,

Best method of operating through the water table in unconsoladated lake sedements.2klm x 1klm block x 70mtrs
Discription; Top 0.5mtr sand @> 1mpa
Remainder to 70mtrs is high water clay/slurry.
Ore body 70--450mtrs.(drill&blast)
Problems; Pit slope stability
Extraction method
Dewatering etc

This is a real brain teaser,
If we dewater during prestrip ,it will eliminate some methods
If there is any traffic on the top 0.5mtrs at more than 2psi ground pressure,the crust breaks up and forces water to the surface , ultimately you have a 70mtr deep bog.
Dredging has it's merits, but bench & slope stability are a real issue.
Dewatering is massive , very large aquafier.
Draglines , no stable land to work from.
Geotecnics still under way.

I have worked in permafrost areas, this deposit is in a hot desert area , so no help from nature.

Orebody mining is another issue because of depth , stability & method.

I'm all ears!!
Water intrusion is massive through all seasons.

RE: Waste removal of 100million/t of overburden,

How about using the water you have available in the aquifer to turn the material to a slurry and sludge pumping it away. If you're in a desert could you pump the slurry to a settling lagoon for drying before carting away in trucks.

Or, depending on environmental considerations, how about adding either lime or cement to stabilise the sediments. This may be a problem if the aquifer is fro drinking water supplies.



RE: Waste removal of 100million/t of overburden,

Have you thought about dredging, discharging into either
settling ponds or the possiblity of a belt press. The
latter would add increase of cost by use of polymer but
would allow you a transferable product. By using a
material such as black driscoll pipe as a discharge you
will gain rigidy and light weight to assist in bank
stabilty. What is your time factor?

RE: Waste removal of 100million/t of overburden,

Whith the ammount of overburden you need to remove and the high water concerns an underground operation might be feasible if the ore body is consolidated enough to sacrifice some upper portion to act as a barrier.

Then you would probably want to drive a slope starting at the perimeter of the aquifer, if feasible.

RE: Waste removal of 100million/t of overburden,


You might want to consider looking from the other direction.
Can you access from u.g. and work upwards. Would need to
evaluate pillar required ( value of ore lost ) to the cost
of removing what you have above as it appears to be a major
undertaking. Do some order of magnitude first to see what
the economics would look like. By your description the slope
stability could be a major problem, that means excavating
to a low angle, meaning lots of material to move. I'd have
a look from the bottom up.

RE: Waste removal of 100million/t of overburden,

Up here this would not be a problem, but I presume that your climate excludes freezing the lake.  Try out the tips at www.drillersclub.com. ; Website is run by Atlas Copco but is open to all.

RE: Waste removal of 100million/t of overburden,

I have seen successful mining in similar environments by :

1 excavate or dregde a hole in the centre of the area (lowest point) to be mined to a level deeper than final design, install pumps to dewater

2 dividing the areas into sections, dig large drains (similar to a moat) around them and linking them together so they drain to the lowest point

3 depending on the success of dewatering either:

a) excavate top sections of cells, this will allow other cells to be drying and excavate on a cell by cell basis and progressively deepen

b) excavate cells in their entirety (below grade if possible) using waste to build a permanent elevated roadway into areas to be mined and also to create embankments to control water flow

Depending on the length of mine life, it may be worth looking at a number of dewatering bores installed outside the pit perimeter to reduce water level inside the pit area

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