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Amount of rock dust displaced by drilling?
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sammatt


Nov 29, 2003, 10:42 AM
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Amount of rock dust displaced by drilling?
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Here's an odd question:

I'd like to know how much rock dust is displaced by the average bolt hole for, say, a 3/8" by 3 3/4" bolt, or a 1/2" by 3" bolt. Does anyone either have access to, or know where I could get access to, any data along those lines?

I apologize if this has already been brought up at RC.com. Any help is appreciated.

Matt


mark_e_wallace


Nov 29, 2003, 10:47 AM
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Re: Amount of rock dust displaced by drilling? [In reply to]
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Wouldn't it just be the volume of the bolt's cylinder?

3.14(r^2)*(length of bolt)

- Mark


andypro


Nov 29, 2003, 11:37 AM
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Re: Amount of rock dust displaced by drilling? [In reply to]
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In reply to:
Wouldn't it just be the volume of the bolt's cylinder?

3.14(r^2)*(length of bolt)

- Mark

It would eb very close to that, but the unconsolidated nature of the dust means theres alot of air in it as well. So the volume of dust would be higher than jsut the volume of rock displaced by the hole. I dont know how muhc higher, it would all depend on the grain size of the dust, and the volume it was measured in.


boltdude


Nov 29, 2003, 12:35 PM
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Re: Amount of rock dust displaced by drilling? [In reply to]
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Those are odd bolts lengths for the diameter.

Calculate it out for straight volume, there won't be a significant difference. Drill bit tips are a bit pointed so there's a little crater in the end of the hole past the end of the newly installed bolt. Some cratering at the surface can be expected, although that's usually little chips instead of dust.

Anyway, the main point for those doing any drilling is to make sure to blow the dust away. Leave it there, and you risk permanently scarring the rock & killing lichen (depending on a lot of factors especially the intensity of the next rain, but it's not worth the risk of leaving it there).

When replacing bolts in Red Rocks, we spend more time blowing dust away than we do pulling the old bolt, drilling out the hole, and placing and tightening the new bolt combined (white rock dust, dark rock, tons of little edges catching the dust, plus a lot of dust since we use large bolts).


petsfed


Nov 29, 2003, 1:48 PM
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Re: Amount of rock dust displaced by drilling? [In reply to]
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In reply to:
In reply to:
Wouldn't it just be the volume of the bolt's cylinder?

3.14(r^2)*(length of bolt)

- Mark

It would eb very close to that, but the unconsolidated nature of the dust means theres alot of air in it as well. So the volume of dust would be higher than jsut the volume of rock displaced by the hole. I dont know how muhc higher, it would all depend on the grain size of the dust, and the volume it was measured in.

Wouldn't it be easier to (aside from simple bolt volume) get a total mass of dust displaced times the average density of the rock? Or am I overthinking this?


andypro


Nov 29, 2003, 4:29 PM
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Re: Amount of rock dust displaced by drilling? [In reply to]
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In reply to:
Wouldn't it be easier to (aside from simple bolt volume) get a total mass of dust displaced times the average density of the rock? Or am I overthinking this?

Yeah. You're way would be a whole lot easier. :lol: I just enjoy complicating things :wink:

If I ahd it my way, I'd go by the average molecular weight of the components of the specific type of rock, the average content of the conglomerate, and the volume of the excavated rock.

I'm also that guy who keeps his calculator set to 15 decimals and writes them all down on a test :lol:


charley


Nov 29, 2003, 5:13 PM
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Re: Amount of rock dust displaced by drilling? [In reply to]
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This is all very interesting but, what is the need or use for this info after you have figured it out.


overlord


Dec 2, 2003, 4:31 AM
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In reply to:
This is all very interesting but, what is the need or use for this info after you have figured it out.

thata exactly what i was wondering...


climb_plastic


Dec 2, 2003, 5:28 AM
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Re: Amount of rock dust displaced by drilling? [In reply to]
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In reply to:
Wouldn't it be easier to (aside from simple bolt volume) get a total mass of dust displaced times the average density of the rock? Or am I overthinking this?

I think that everyone is overthinking this just by responding. I'm overthinking this just by wondering who cares and why.


unabonger


Dec 2, 2003, 1:49 PM
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I apologize if this has already been brought up at RC.com. Any help is appreciated.
Matt

Apology not accepted. This one was answered in the first week in a hijacked thread titled "The Volume of Colonic Summer Sausage Displaced During Homoerotopathic Activity"

And god knows no one ever repeats good solid questions like yours!

The MetroBonger


sammatt


Dec 2, 2003, 2:47 PM
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Doh, Una(Metro)Bonger, you almost had me!

Wouldn't it be interesting to say, compare and contrast the amount of rock displaced by bolts at a giving climbing area versus the amount of rock displaced by tunnels through that climbing area?

Colonic Summer Sausage. This sounds familiar. I was once poisoned by the Gay Indigenous Tribe of Turtle Island (should have washed my hands). at the Fingerbanger Boulder of Camp Dick. True story. Names not invented. Does summer sausage figure into this somehow?

Peace


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