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Blasting Frozen Muck

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Kurt...

  I played with it a couple seasons years ago. Worked well in specific situations. I am definitely not one

to give advice on the subject though!

 

 MIRL put out a video, back in the early 80s I believe, on blasting frozen muck. I had a copy but dang

if I can find it. You might see if you can locate a copy.

 

Remember ... you have to have something to remove the waste.

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Dick / Geo / Flint ( Kurt ) -

 

Quote: " Tophole Drilling my Permafrost Placer ". I also assumed that the reference was to Drilling & Blasting the Overburden covering a surface Placer deposit. Maybe I read it wrong. I can also understand Geo's reference to working an Underground / Deep Placer as Flint's earlier Topic entitled " Anfo usage & Regulations " seemed to be dealing specifically with Blasting in his Shaft or in his Drifts which indicated that the Blasting itself was potentially going to be taking place Underground. ( Down a Hole )   

 

I weigh in on this only because I have a Surface Blasting Licence and have been a " Shotfirer " in Open Pit Mines. Although I would be the first to admit that the Blasting of Permafrost would be a real challenge. Given that I don't have that depth of overburden to worry about, at least where I hopefully one day will be Mining, I haven't needed to give it any thought but the discussion of it has come up from time to time so I find it a really interesting subject.

 

Is there any general information that you can give us Flint / Kurt with respect to the Depth of the ground / muck / overburden you are thinking about Blasting ? i.e. Do you have any idea yet of the profile of your Placer in relation to where your pay gravels sit from surface to Bedrock ?  Will you have access to any particular type of Drill ?

 

I am also interested to see what the experienced guys come up with but at the end of the day it's probably going to boil down to the practicalities / advantages of the exercise vs the Economics of it. 

 

Steve.        

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Well, I guess I should have made myself a bit more clear.  We're not talking shaft sinking here.  I got a shaft already.  Nor am I thinking drifting with anfo...though I know someone who has done that.  This will be open cut mining...removing 58' of frozen muck to expose the gravel.  I'm envisioning using a 2 man, gas operated core or auger drill to put down blast holes maybe 10 deep for a section of ground, the dimensions of which are to be determined though study and even trial and error [as I have never heard of this being done].  We'll have a dozer push the blasted muck to where a dragline can remove it from the cut.  Geo, your concern for the refreezing of the blasted muck is valid, I believe.  We'd just have to make sure we didn't take too big a cut that the dozer couldn't handle in time before it refroze. 

   Thanks for the input thus far and I look forward to further discussion.

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Yup, Chuck...we do have 58 feet of good ole' muck.  I'm not up on all the fine points of dragline positioning so I can't talk about their use with any confidence.  I'm guessing that our cuts are going to be wide enough [across valley] that the dragline won't be able to reach the furthest blasted overburden, hence the reason for the dozer.  Years ago I worked as a welder for a strip coal mine in Montana.  We had an 80 cy walking dragline that was fascinating to watch.  If this all works out it will be an amazing learning experience. 

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Fluffing the muck up with charges and moving it immediately with a dozer sounds hopeful.

 

Are flaw fields like they used for bucket dredges illegal now? That process probably takes too much time but might work with a dragline.

 

Kurt William (Kinda nice to need to use my middle name again.I miss my uncle and cousin.)

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Kurt William,

   Flaw fields...   Is that where they drove large numbers of steam points in the frozen ground?

One problem we have at the claim is limited water.  If we can get a good dam and holding pond built, we'll have sufficient water for steaming.  Also considering bringing in water from a large spring about a half mile away.  We'd also have to acquire a monster boiler.  It's an interesting process to consider if blasting proves not doable.

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Did some blasting of frozen peat and muck when I was a combat engineer at Ft Richardson. Saturated frozen ground is springy. So higher brissance is needed to get a decent shatter and throw (slight heave just refreezes quickly). The number of shots will be far higher than on unfrozen ground. The costs will be high.

Is there a reason you wish to avoid drifting?

I ask this for another reason. All 58' of muck is gonna have to be stockpiled somewhere and that cost will be butt ugly high. Then when it comes time to rehab, you get to pay that cost again. Neither coming or going with the muck returns a profit, only losses. But wait!! It gets worse. That stockpile will freeze resulting in the need to bust it up again before you move it back to where it came from.

Then there is the possibility that the paystreak may be narrow. Cutting a 58' deep trench a few hundred yards long to access a comparatively narrow paystreak will definately run up costs.

Let's run some math. we can round 58' up to 20 yards. Call the blade width 4 yards and the length of the cut 250 yards. 20X4X250 = 20,000 cubic yards. That is roughly equivalent to a cube 27 yards to the side. But of course it is prohibitively expensive to stack overburden that high, so let's say trapezoidal cross section 5 yards high, top flat at 5 yards and an angle of repose at 20°. That make a cross section of about 95 square yards. We'll round to 100 sq yds because this is ballpark calcs anyway. 20,000 cu yds/100 sq yds means a stockpile 200 yards long with a cross section base width of roughly 32-33 yards.

eric

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Eric,

   Really appreciate your input.  Some real good things to think about.  We would undertake the open cut method only after a thorough drill program to determine if there is enough gold to make it worth while.  I just decided to draw out a possible mining design plan to get a more realistic understanding if this whole thing could be physically possible.  I now think that, based on the nature of muck, it would be impossible to open a cut 70' deep [to include about 2' of bed rock] using a 250 yd/hr dragline [what might be available to us].  My way of figuring goes like this:  drill and blast a 30' x 10' x 100' pattern, clean it out, move downstream 30', blast and clean out the next top cut.  Move back upstream, blast and clean out a 30' x 10' cut in the bottom of the top cut.  That would leave approximately a 10' wide bench above each side of your bottom cut.  I figure you'd need it that wide to account for sliding due to thawing muck.  So now you'd go back downstream and take another 30' top cut, move over and take another 2nd tier cut.  Now you have a pit 20' deep and 50' wide at the bottom.  Blast and remove the next 30' x 10' in the middle of the pit.  I'm down only 30' and I have a pit 90' wide at the top.  That's already a cast of at least 100' and I'm not even half the depth to the bottom.  Extend it all out and to be able to have a 20' wide cut at the very bottom in bed rock, my pit at the top would be 1/3 mile wide!!!  Talk about the Grand Canyon!  The largest walking dragline in existence doesn't have the capability of casting material that far...almost 1000'!  Now, say all that were even possible to pull off, I'd need to start working on the next section downstream, but where to put that material?  I can't begin back filling the pit till I get at least 3, 20' bottom cuts removed, which means removing an additional 45,000 cu yds of muck and WHERE to put it???  Unless I'm totally off base, I can't see any way on God's green earth that it could work.  And I haven't even begun to figure in all the other headaches like creek and ground seep drainage, fuel and blasting agent costs, road access into the claim, repairs on heavy equipment and the fact that all the drilling, blasting and removal of material must take place in the cold weather months.  Uggggh!  I'm back to liking the idea of drifting out of a shaft...just like they did it back in the day. 

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Quote: geowizard

"The single, unavoidable concern with muck (aka mud) is the fact that the slope of natural repose is horizontal. A vertical wall of muck will become liquid and mud will slide to the lowest level possible. Usually, the lowest level is the bottom of the hole."

I overlooked this aspect. We did most our demo training in the winter.

All the costs were borne by the US taxpayers, so I wasn't and still ain't qualified to estimate the cost of blasting.

However the point about thawing made by geowizard will be a brutal reality come every summer. Slumping of the muck can run the gamut from oozing to quite sudden releases of big-time yardage. With the angle of repose just slightly greater than 0°, the slump could occur some distance away from any worker in the trench and rapidly overtake them ala mud/debris flow. This would make working in the trench seriously hazardous during thaw periods.

Staying safe is relatively cheap compared to the alternatives.

eric

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I'm by no means an expert on the dynamics of thawed muck.  However, I have learned that muck varies in water content.  My partner had drifts that contained large ice lenses and apparently high water content in general.  The muck I have so far dug up and stacked on my claim seems to have much less water content.  As it sits in the sun and thaws it barely changes shape...just dries out like normal mud.  Still and all, I respect your concerns for major slumpage and I would expect that even in the best of circumstances, we would experience problems with it.

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.  However, I have learned that muck varies in water content. 

 

  Kurt... good observation and very true. I only have 25' of muck to deal with, but it is very 'wet' muck. Riddled

with ice lenses.

      Most of the guys I know/knew that were stripping deep ground have at one time tried the muck removal

method you proposed. It can and does work, but most guys just went back to ripping with a Cat or excavator.

   

   Unfortunately most of us can't use the preferred method of hydraulicing. So we are left with methods that may be

less than desireable and more costly. What works best for you is going to be trial and error.

 

  After you drill it and find the values you have, then comes the time to consider an overburden removal

system.  I would not completely dismiss your idea, but I would urge you to talk with some miners that have

 far more real world experience.

 

 The little I did was small areas. Mostly stubborn places that just didn't want to thaw. I used cold water and points

for the holes. It was very effective at the time. Now I can pretty much do the same with my 300 class excavator.

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Kurt,

This is why many deeper placers were abandoned. When hydraulicing was shut down, the new costing for over-burden removal greatly exceeded the profit potential.

Drifting by hand was limitted by acceptable depth and pucker factor. Acceptable depth was determined by water infiltration, encouraging samples, the determination of the individual miner, financial resources and quite often partners. There are other reasons as well. On 19 Below on Crooked Creek in the old Nelchina District, a shaft was sunk to 180 feet one summer and plans were to go to bedrock that winter. The prospectors logged the sediments all the way down as reported in USGS Bulletin 668, 1918.

I,uh, remember that tidbit every time I see hard work before me. An example of the "ant moving the rubber tree plant". Buck up and be of good cheer. You now know what can be done and what is practical. Truth be told, you are way ahead of the pack.

Many operations are run on "hopium" and a full-time job elsewhere. When it has to be said over and over again, "an effective sampling plan can make or break an operation" it becomes obvious that few listen. Ergo their sampling program might be find color, start mining. If recovery is too low to be profitable after several week-ends expended, move over there and try again. "Hope" over there is not an effective sampling strategy.

eric

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Doug Baker, outside Manley, has a large hydraulicing operation.  As I recall, his overburden is at least 60', but, whereas, he has plenty of water from Quartz Creek, I have very little.  Also, he has significantly better gradient than has my ground which aids in the wash.   Several years ago I helped set up a small hydraulic system in Eureka.  I didn't get much time on the "giant" but what I did sure was fun.  But we digress...

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