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sixleggedinsect
Apr 26, 2006, 8:23 PM
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Looking up bolt specs online, a lot of them rate differently based on the different types of concrete.
Is there any conventional wisdom on the comparisons between various rock types and concretes?
Ie: might one expect a bolt in yosemite granite to have similar post-placement specs to 3000 PSI concrete? 5000 PSI?
good sandstone (most redrocks)? bad sandstone (arches)? limestone?
thanks,
anthony
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caughtinside
Apr 26, 2006, 8:30 PM
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Hmm, I always thought you looked at the shear strength of a bolt.
With regards to rock type, harder rock would accept wedge bolts (less surface area on side of hole) while softer rock you need expansion bolts, which would place more surface area on the side of the hole.
Too soft, and you need glue ins.
Sorry I can't help more directly answer your question. But as a rule of thumb I'm more concerned with the rock blowing than the bolt shearing. Are you thinking more of pullout strength?
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sixleggedinsect
Apr 26, 2006, 8:35 PM
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In reply to: Hmm, I always thought you looked at the shear strength of a bolt.
that's just what i'm trying to get at. rated shear strength differs based on rock/concrete quality. for instance, look at
http://www.ramset-redhead.com/trubolt_perf_1.asp
so, as an example, for a 3/8" x 3.75" ramset wedge anchor, what shear strength would you expect in yosemite granite? red rocks sandstone? potrero limestone?
anthony
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sixleggedinsect
Apr 26, 2006, 8:46 PM
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just found this:
http://safeclimbing.org/education/mechbolts.htm
which helps a bit. but im still curious,
anthony
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j_ung
Apr 26, 2006, 8:46 PM
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Somebody posted test results on both shear and pullout strength for various types of bolts in soft sandstone just a couple weeks ago, but I can't remember where it is. Some of the results were surprisingly weak. Sorry I can't be of more help.
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sed
Apr 26, 2006, 9:01 PM
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i have seen those charts too. i presume most of the rock i bolt in to be either the middle range psi concrete or even the low range one. the highest psi concrete is very hard and also reaches a uniformity that rock rarely does. However, if you go with the powers powerbolt you can't go wrong in terms of strength. always demand at least grade 5 steel no matter what kind you get.
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j_ung
Apr 26, 2006, 9:12 PM
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I'm constantly reminded of how lucky I am that I live in the SE, land of bullet sandstone.
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sixleggedinsect
Apr 26, 2006, 9:28 PM
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In reply to: Somebody posted test results on both shear and pullout strength for various types of bolts in soft sandstone just a couple weeks ago, but I can't remember where it is. Some of the results were surprisingly weak. Sorry I can't be of more help.
thanks for the link. it is intersting, but mostly irrelevant to the types of anchors most folks around here use. they use almost exclusively glue-ins in the test, and state that their sandstone is particularly bad.
is anyone familiar with the rock cited in the test? is it similar to something i would have climbed on?
the study references comparisons between rock/concrete in terms of PSI ratings on the powers.com website, which would be great, but i cant seem to find the information.
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redpoint73
May 1, 2006, 7:48 PM
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If you are talking about 3000 or 5000 psi concrete, I presume you mean compressive strength, since that is typically how concrete is specified in the construction industry (or sometimes in 'bags' of cement per cubic yard). Of course, compressive strength has little to do with bolt strength.
Strength of rock is obviously going to be very dependent on the rock type, weathering, joints and fractures, and other factors. As far as compressive strength, I have seen unweathered, quarried limestone and granite fail at well over 10,000 psi. Now, I wouldn't go by that when placing a climbing bolt. The post above that recommended using the middle or low range of concrete is probably a nice, conservative way to go.
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sketch
May 12, 2006, 6:27 PM
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Also check out the bolting guide that Rick Weber wrote. It's got some information on the material properties of different types of rock (such as compressive ultimate tensile strength).
http://www.muirvalley.com/pdf/BoltingRed12.pdf
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coolklimber
May 18, 2006, 9:09 PM
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A bolt is only as strong as the rock it's in.
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sixleggedinsect
May 29, 2006, 2:44 AM
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In reply to: A bolt is only as strong as the rock it's in.
um, yes. which is why i was asking about how strong the rock is.
sketch, thanks for the links.
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billcoe_
May 30, 2006, 12:50 AM
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Great link Sketch!
Seeing the evidence that they think the Corbin Sandstone is approx 2000 psi, based on how they describe it, a guess would seem to suggest that Basalt might be @ 4000 and Yosemite Granite at least 6000 psi.
Interesting to note that variations in some areas can be huge. The tuft at Smith Rocks, for instance, can vary from chalk you can crush with your hand (easily less than 1000) to fairly solid stuff that might be 3000-4000 psi. Castleton also has some sections of sandstone that look something like stalgtites/weathered quartz.
All rough guessrotimates of course.
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norushnomore
Jun 1, 2006, 9:15 AM
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Sounds like your real question is it ok to use TrueBolt (wedge style) instead of Power's PowerBold (sleeve style) or Fixe wedge bolt as the first one can be found for some 80c for SS-3/8x3.0
Well you can simply compare specs for both at the same PSI level:
PowerBolt is stronger but not by much in the worst case (2000)
but by whole lot more at 6000
My opinion TrueBolt is plenty aceptable, just make sure they are in SS:
UIAA 123 standard limit for rock anchors is 20 kiloNewtons and TrueBold in 3/8x3.0 is at about the same number as well for 4000 and higher PSIs
(no good for sand stone)
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chossmonkey
Jun 11, 2006, 12:28 AM
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In reply to: Looking up bolt specs online, a lot of them rate differently based on the different types of concrete. Is there any conventional wisdom on the comparisons between various rock types and concretes? Ie: might one expect a bolt in yosemite granite to have similar post-placement specs to 3000 PSI concrete? 5000 PSI? good sandstone (most redrocks)? bad sandstone (arches)? limestone? thanks, anthony
Bolt manufacturers don't test in concrete that is as soft as "soft" rocks. The concrete would be way to soft for construction purposes. Use bolts 4-6 inches long with a diameter of 1/2 inch in all soft rock. In really soft rock wedge bolts can work better than sleeve bolts which may not tighten. Sleeve bolts with a stud head would probably be the best mechanical bolt for super soft rock if it wasn't for the fact that they are generally much weaker than the hex head sleeve bolts. For soft rock you should seriously consider learning how to properly install glue-in bolts.
Medium rock would be similar to the 3000psi concrete.
Hard rock would be similar to 5000psi.
Keep in mind that rock strength can very greatly no matter what the rock type. Sometimes in the same formation, whether it is sandstone or granite.
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