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French climber and prolific route equipper Bruna Fara, has reported a worrying incident on Kalymnos. His wife Renee Guerin led a recent route on North Cape - Reise (7a) which was put up by the Remy brothers in April this year. As she was lowering off, the tension on the rope pulled the 5th bolt...Read more at http://www.ukclimbing.com/news/item.php?id=64604
In reply to UKC News:
I think it's a bit poor for people to still be putting routes up on expansion bolts when glue-ins are so superior. Particularly on a coastal limestone in a hot country.
I know they're cheaper but if you're willing to go to the effort to establish new routes it should be done in the best style. I've seen a lot of truly terrible crap done with expansions so i'm a little bias but I just don't think there's room for them anymore. A glue in last longer than a expansion, as climbers we should be responsible for taking care of the rock for the future. Nothing pisses me off more than when you start to see clusters of bolts because people are too stingy to do it right the first time round
...../rant
I think it's a bit poor for people to still be putting routes up on expansion bolts when glue-ins are so superior. Particularly on a coastal limestone in a hot country.
I know they're cheaper but if you're willing to go to the effort to establish new routes it should be done in the best style. I've seen a lot of truly terrible crap done with expansions so i'm a little bias but I just don't think there's room for them anymore. A glue in last longer than a expansion, as climbers we should be responsible for taking care of the rock for the future. Nothing pisses me off more than when you start to see clusters of bolts because people are too stingy to do it right the first time round
...../rant
In reply to Jon_Warner:
"The stainless steels used today in almost all climbing bolts are susceptible to a failure mechanism called Chloride Stress Corrosion Cracking or SCC. Just like it sounds, the chlorine ion, which results from dissolving salt in water, and stress must both be present. A typical multi-piece expansion bolt has the shaft in tension, and the hanger has complex stresses placed on it when it is clamped against the rock as you tighten the nut. This type of bolt placed in a sea cliff is a bomb with a short fuse. Once started, SCC spreads like a disease following the stress lines in the steel, much like grass grows in small cracks in concrete and forces the pieces apart. The cracks get larger over time, and soon the microscopic grains of the metal are no longer in contact."
from http://www.safeclimbing.org/education/deepbluesea.htm
"The stainless steels used today in almost all climbing bolts are susceptible to a failure mechanism called Chloride Stress Corrosion Cracking or SCC. Just like it sounds, the chlorine ion, which results from dissolving salt in water, and stress must both be present. A typical multi-piece expansion bolt has the shaft in tension, and the hanger has complex stresses placed on it when it is clamped against the rock as you tighten the nut. This type of bolt placed in a sea cliff is a bomb with a short fuse. Once started, SCC spreads like a disease following the stress lines in the steel, much like grass grows in small cracks in concrete and forces the pieces apart. The cracks get larger over time, and soon the microscopic grains of the metal are no longer in contact."
from http://www.safeclimbing.org/education/deepbluesea.htm
In reply to UKC News:
I am living and bolting in Thailand near Bangkok and I only use glue-in's. I was amazed to see that people are still using expansion bolts on limestone by the coast!!! After all the researched that has been conducted, isn't it common sense to use glue-in's with Hilti RE 5OO glue????
I am living and bolting in Thailand near Bangkok and I only use glue-in's. I was amazed to see that people are still using expansion bolts on limestone by the coast!!! After all the researched that has been conducted, isn't it common sense to use glue-in's with Hilti RE 5OO glue????
In reply to rickeden:
Glue-ins are a pain on steep routes bolted from the bottom and even I resort to bolt-ins for this. Also the culture of more new routes on ones tick list and the ethical standpoint of some climbers of only opening routes from the bottom means glue-ins aren´t so attractive either.
There are regrettably a lot of crap bolts out there on the market and I have just this morning wasted 2 hours of my life testing and rejecting a new delivery of apparently satisfactory bolt-ins which don´t in anyway conform to any known standard. 9.6kN really isn´t good enough when a comparable European quality bolt will get 38kN and the requirements for EN959 are 15kN and 25kN.
Glue-ins are a pain on steep routes bolted from the bottom and even I resort to bolt-ins for this. Also the culture of more new routes on ones tick list and the ethical standpoint of some climbers of only opening routes from the bottom means glue-ins aren´t so attractive either.
There are regrettably a lot of crap bolts out there on the market and I have just this morning wasted 2 hours of my life testing and rejecting a new delivery of apparently satisfactory bolt-ins which don´t in anyway conform to any known standard. 9.6kN really isn´t good enough when a comparable European quality bolt will get 38kN and the requirements for EN959 are 15kN and 25kN.
In reply to UKC News:
yups. You dont even have to fork out top dollar for the titanium (tonsai perhaps being the exception) in less hostile environments I think stainless/marine grade stainless with the Hilti RE 500 Glue is still a magnificent improvement on expansions.
They made a documentary called the Titanium Project about the science/safety behind bolting. Makes for some interesting watching. Blew my mind, perfectly placed expansions failing under body weight in 3 months due to corrosion :/
I know glue - in's are a pain on steep ground but it's definitely doable, just more of a hassle. I helped a guy bolting a roof climb with glue-ins, it worked it just wasted a bit extra glue
yups. You dont even have to fork out top dollar for the titanium (tonsai perhaps being the exception) in less hostile environments I think stainless/marine grade stainless with the Hilti RE 500 Glue is still a magnificent improvement on expansions.
They made a documentary called the Titanium Project about the science/safety behind bolting. Makes for some interesting watching. Blew my mind, perfectly placed expansions failing under body weight in 3 months due to corrosion :/
I know glue - in's are a pain on steep ground but it's definitely doable, just more of a hassle. I helped a guy bolting a roof climb with glue-ins, it worked it just wasted a bit extra glue
In reply to Kemics:
can't find the film but here's their web page - scary ThaiTanium Project
http://thaitaniumproject.com/?page_id=2
can't find the film but here's their web page - scary ThaiTanium Project
http://thaitaniumproject.com/?page_id=2
In reply to UKC News: Last september I was climbing by the caves of Totem sector, at Telendos island in Kalymnos, I am no expert but the state of some bolts seemed poor to say the least (rusty nuts and bolts). It looked as if the rock seeps a lot during the winter and rottens the bolts. I never assume that a route is safe just because it has bolts and always visually check the state of the fixed gear before committing to it.
In reply to UKC News:
The crazy thing as well to think about, usually the hanger can be nice and shiny but internally the bolt can be completely rotten. So if the hanger and external part of the bolt have corroded, potentially the internal could be extremely compromised.
The crazy thing as well to think about, usually the hanger can be nice and shiny but internally the bolt can be completely rotten. So if the hanger and external part of the bolt have corroded, potentially the internal could be extremely compromised.
In reply to UKC News: It would be good to know why these bolts were recalled, and what type of stainless steel was used for the hangers and bolts. Does anybody have any info on this?
In reply to duzinga:
Pretty obvious why the bolts are being recalled, they corrode and break.
The guys at Rocklands know what stainless they used for the hangers since they made them (usually they use 1.4401), as it says in the article the hangers are not a problem.
You need a material analysis to know what the bolt material is and what help is that? In Rocklands position I wouldn´t pay for the lab costs either since it is clearly not what it was claimed to be so the results are purely academic.
Pretty obvious why the bolts are being recalled, they corrode and break.
The guys at Rocklands know what stainless they used for the hangers since they made them (usually they use 1.4401), as it says in the article the hangers are not a problem.
You need a material analysis to know what the bolt material is and what help is that? In Rocklands position I wouldn´t pay for the lab costs either since it is clearly not what it was claimed to be so the results are purely academic.
In reply to jimtitt: So a dodgy supplier of raw materials that would have caused problems even if the bolts were glue-ins.
In reply to UKC News:
Have any of the people who are complaining about bolting standards contributed to the local bolt funds?
Have any of the people who are complaining about bolting standards contributed to the local bolt funds?
In reply to duzinga:
Naturally, which is why the manufacturers are generally careful to only use European sourced material and test the product as well especially with a new batch of material. The guys at Rocklands (who I know) have considerable experience and know the problems with imported stainless steel as well as I do but with bought-in products the country of origin is generally not declared and then some testing is in order, even if they are stamped as made in the EU there is no guarantee this is actually so.
Naturally, which is why the manufacturers are generally careful to only use European sourced material and test the product as well especially with a new batch of material. The guys at Rocklands (who I know) have considerable experience and know the problems with imported stainless steel as well as I do but with bought-in products the country of origin is generally not declared and then some testing is in order, even if they are stamped as made in the EU there is no guarantee this is actually so.
In reply to jimtitt: Thanks for clearing that up Jim.
In reply to Jamie Bankhead:
Yes. That's why i've only used Fixe bolts because every individual bolt is tested to half strength before it leaves the factory (I think) and they have incredibly high levels of QC. Plus with the Hilti RE 500 resin it also acts as a protective layer around the bolt as well which helps further to prevent corrosion. (unlike some of the earlier trails with different resins which were still water-permeable)....i'm a bit of a gear nerd so find it quite interesting
> (In reply to UKC News)
>
> Have any of the people who are complaining about bolting standards contributed to the local bolt funds?
>
> Have any of the people who are complaining about bolting standards contributed to the local bolt funds?
Yes. That's why i've only used Fixe bolts because every individual bolt is tested to half strength before it leaves the factory (I think) and they have incredibly high levels of QC. Plus with the Hilti RE 500 resin it also acts as a protective layer around the bolt as well which helps further to prevent corrosion. (unlike some of the earlier trails with different resins which were still water-permeable)....i'm a bit of a gear nerd so find it quite interesting
In reply to Kemics:
I think you might like to check that by contacting Fixe!
Plus with the Hilti RE 500 resin it also acts as a protective layer around the bolt as well which helps further to prevent corrosion. (unlike some of the earlier trails with different resins which were still water-permeable)....i'm a bit of a gear nerd so find it quite interesting
No bolt manufacture gives any credence to the concept of encapsulation and the requirements for corrosion resistance are purely related to the material. Anyone who has pulled a lot of bolts knows encapsulation is an unreliable concept at best and not to be relied on to protect the bolt.
> (In reply to Jamie Bankhead)
> [...]
>
> Yes. That's why i've only used Fixe bolts because every individual bolt is tested to half strength before it leaves the factory (I think) and they have incredibly high levels of QC.
> [...]
>
> Yes. That's why i've only used Fixe bolts because every individual bolt is tested to half strength before it leaves the factory (I think) and they have incredibly high levels of QC.
I think you might like to check that by contacting Fixe!
Plus with the Hilti RE 500 resin it also acts as a protective layer around the bolt as well which helps further to prevent corrosion. (unlike some of the earlier trails with different resins which were still water-permeable)....i'm a bit of a gear nerd so find it quite interesting
No bolt manufacture gives any credence to the concept of encapsulation and the requirements for corrosion resistance are purely related to the material. Anyone who has pulled a lot of bolts knows encapsulation is an unreliable concept at best and not to be relied on to protect the bolt.
Hi Jim,
Thanks for all your sound technical background.
A question though: in a perfect world what, in your view, would be the best bolt solution for Kalymnos, from a sustainability (and safety) viewpoint. Would much appreciate your advice.
Carl
Thanks for all your sound technical background.
A question though: in a perfect world what, in your view, would be the best bolt solution for Kalymnos, from a sustainability (and safety) viewpoint. Would much appreciate your advice.
Carl
In reply to jimtitt:
From a novice just trying to get an idea about this.
Is the reason why glue-in bolts aren't ideal for all applications because they have to be held in place to set or what?
Noting that the constant tension in the bolt appears to be an issue with crack expansion and spreading, would a combination approach of gluing expansion bolts be viable?
ie. If you put a expansion bolt in with glue only expanding the bolt enough to hold it in place so that the glue could set.
From a novice just trying to get an idea about this.
Is the reason why glue-in bolts aren't ideal for all applications because they have to be held in place to set or what?
Noting that the constant tension in the bolt appears to be an issue with crack expansion and spreading, would a combination approach of gluing expansion bolts be viable?
ie. If you put a expansion bolt in with glue only expanding the bolt enough to hold it in place so that the glue could set.
In reply to gethin_allen:
afaik there isn't a situation where resin bolts wont stick (the resin is way too viscous to be pulled out by gravity). It's tricky because on expansion the bolt is good to go instantly so you can clip off on it to set up your rigging so you can place the next bolt. Whereas with a resin bolt, you have to let the resin set, the manufactures recommendations vary from a few hours plus, but i think most people leave 24 hours to be on the safe side to let it set. Not a problem on horizontal climbs but this means if you're bolting a step climb you have to clip a load of trad gear/sky hooks to keep you in place while bolting with rigging that is kind of similar to reverse aiding a pitch.
"No bolt manufacture gives any credence to the concept of encapsulation and the requirements for corrosion resistance are purely related to the material."
I know the encapsulation isn't relied on to protect the bolt but I'm fairly sure it's accepted that it helps. My knowledge only comes from bolting in Thailand so it might be different. But on Tonsai particularly i know they moved from the earlier resins to the Hilte RE 500 because it wasn't water permeable. I might be wrong, that's just what I learnt from the guys I was bolting with.
afaik there isn't a situation where resin bolts wont stick (the resin is way too viscous to be pulled out by gravity). It's tricky because on expansion the bolt is good to go instantly so you can clip off on it to set up your rigging so you can place the next bolt. Whereas with a resin bolt, you have to let the resin set, the manufactures recommendations vary from a few hours plus, but i think most people leave 24 hours to be on the safe side to let it set. Not a problem on horizontal climbs but this means if you're bolting a step climb you have to clip a load of trad gear/sky hooks to keep you in place while bolting with rigging that is kind of similar to reverse aiding a pitch.
"No bolt manufacture gives any credence to the concept of encapsulation and the requirements for corrosion resistance are purely related to the material."
I know the encapsulation isn't relied on to protect the bolt but I'm fairly sure it's accepted that it helps. My knowledge only comes from bolting in Thailand so it might be different. But on Tonsai particularly i know they moved from the earlier resins to the Hilte RE 500 because it wasn't water permeable. I might be wrong, that's just what I learnt from the guys I was bolting with.
In reply to carl dawson:
Ones paid for by the EU taxpayers like everything else!
Seriously though, we don´t hear reports of mass bolt failure so I´d think what they´ve got is o.k. Aris is pretty clued up and unlikely to let too much rubbish get used and the climate in Kalymnos is pretty bolt friendly as well. Any good 1.4401 (316) should be good there in realistic terms.
For bolt-ins, the alternative and far better HCR (1.4529 or similar) are pricey and hard to get and hangers are unobtainable. For glue-ins the best you can get would be 1.4462 with epoxy-acrylate glue and I discussed with the guys from Rockland about this but they cannot get the material in Greece except at a horrific price (it is special delivery even for me), the alternative is I supply the bolts but this is also expensive and not the purchasing policy there.
Jim
> Hi Jim,
> Thanks for all your sound technical background.
>
> A question though: in a perfect world what, in your view, would be the best bolt solution for Kalymnos, from a sustainability (and safety) viewpoint. Would much appreciate your advice.
>
> Carl
> Thanks for all your sound technical background.
>
> A question though: in a perfect world what, in your view, would be the best bolt solution for Kalymnos, from a sustainability (and safety) viewpoint. Would much appreciate your advice.
>
> Carl
Ones paid for by the EU taxpayers like everything else!
Seriously though, we don´t hear reports of mass bolt failure so I´d think what they´ve got is o.k. Aris is pretty clued up and unlikely to let too much rubbish get used and the climate in Kalymnos is pretty bolt friendly as well. Any good 1.4401 (316) should be good there in realistic terms.
For bolt-ins, the alternative and far better HCR (1.4529 or similar) are pricey and hard to get and hangers are unobtainable. For glue-ins the best you can get would be 1.4462 with epoxy-acrylate glue and I discussed with the guys from Rockland about this but they cannot get the material in Greece except at a horrific price (it is special delivery even for me), the alternative is I supply the bolts but this is also expensive and not the purchasing policy there.
Jim
In reply to gethin_allen:
The problem is steep routes have to be bolted by aiding from below, mostly on the bolts you are setting. If you waited for the glue to set it would be slow, boring and very expensive in glue and nozzles since you´d need a new one every bolt.
Glueing in expansion bolts is realistically out, first none are intended to be glued in and aren´t certified that way,secondly you still need to hold the hanger on so the tension is still there even though the bolt itself is glued in and continous tension on glued bolts is a dodgy business due to glue creep.
Usual practice is to use bolt-ins at first and when they start to show their age use them to allow glue-ins to be placed and chop the old bolts.
The problem is steep routes have to be bolted by aiding from below, mostly on the bolts you are setting. If you waited for the glue to set it would be slow, boring and very expensive in glue and nozzles since you´d need a new one every bolt.
Glueing in expansion bolts is realistically out, first none are intended to be glued in and aren´t certified that way,secondly you still need to hold the hanger on so the tension is still there even though the bolt itself is glued in and continous tension on glued bolts is a dodgy business due to glue creep.
Usual practice is to use bolt-ins at first and when they start to show their age use them to allow glue-ins to be placed and chop the old bolts.
Happy to be corrected here, but isn't it apparent that the example photographed does not appear to be a failure due to corrosion. It looks to me like that bolt has been over-tightened and failed partly due to that. As Jim pointed out, while glue-in bolts are preferable (I used his bolts on Gower a couple of years ago) developing steep routes requires the bolts to make progress so glue just isn't practical until it comes to rebolting. Also worth noting that all this kit often has to be flown out there and expansion bolts are lighter than taking the bolt, glue, nozzles and gun.
In reply to Adrian Berry:
I suggested to Bruno the bolt might have been over-tightened and he was sceptical, saying the Remys have placed thousands of bolts and know what they are doing. He pointed out the corrosion to the nut and the end of the bolt (7 months old and in a dry environment) - and simply said "not Inox".
Chris
I suggested to Bruno the bolt might have been over-tightened and he was sceptical, saying the Remys have placed thousands of bolts and know what they are doing. He pointed out the corrosion to the nut and the end of the bolt (7 months old and in a dry environment) - and simply said "not Inox".
Chris
In reply to Adrian Berry:
I´d agree that the failure doesn´t look like a typical corrosion problem which anyway rarely occurs down at the bottom of the cone but under the hanger. If the bolts are from less ductile or weaker material the normal place they fail is at the cone, not the thread and this looks like one which was tightened and then loaded or overtightened. That the Remys have placed thousands of bolts doeasn´t make them immune, if they though it was a normal stainless bolt and cranked it down like normal but really it was some nasty material they could easily have broken or strained it without noticing. It´s hard to overtighten a normal stainless bolt, you need about 90Nm which is a lot with a little spanner!
Flying out with glue is completely out these days, you might as well write `BOMB´on your luggage! We send it by parcel courier or post to our destination which is also officially not permitted if it goes by air or ship, I´ve had shipments going through Spain refused before now.
Jim
I´d agree that the failure doesn´t look like a typical corrosion problem which anyway rarely occurs down at the bottom of the cone but under the hanger. If the bolts are from less ductile or weaker material the normal place they fail is at the cone, not the thread and this looks like one which was tightened and then loaded or overtightened. That the Remys have placed thousands of bolts doeasn´t make them immune, if they though it was a normal stainless bolt and cranked it down like normal but really it was some nasty material they could easily have broken or strained it without noticing. It´s hard to overtighten a normal stainless bolt, you need about 90Nm which is a lot with a little spanner!
Flying out with glue is completely out these days, you might as well write `BOMB´on your luggage! We send it by parcel courier or post to our destination which is also officially not permitted if it goes by air or ship, I´ve had shipments going through Spain refused before now.
Jim
In reply to jimtitt:
If the bolt snapped due to over-tightening - wouldn't it become loose again and just spin? Or could it conceivable break at a later date because of the continued stress - which presumably would be due to faulty/inappropriate materials, rather than actual over-tightening?
Chris
If the bolt snapped due to over-tightening - wouldn't it become loose again and just spin? Or could it conceivable break at a later date because of the continued stress - which presumably would be due to faulty/inappropriate materials, rather than actual over-tightening?
Chris
In reply to Chris Craggs:
All a bit hard to say because the failure in the photo isn´t the normal one you see, if you overtighten a stainless bolt the normal mode is that the tags on the clip fail and the bolt rotates without tightening any more or more rarely the threads shear at the nut. I´ve only seen one bolt broken at the cone and that was a 16mm steel one which was in some rather soft conglomerate which allowed the bolt to tip over a bit and it snapped at the bottom. Took 58kN to do it though!
Without a really high quality picture of the end of the bolt who can tell? Get out on one of the dodgy routes with a torque wrench and test a few!
Jim
All a bit hard to say because the failure in the photo isn´t the normal one you see, if you overtighten a stainless bolt the normal mode is that the tags on the clip fail and the bolt rotates without tightening any more or more rarely the threads shear at the nut. I´ve only seen one bolt broken at the cone and that was a 16mm steel one which was in some rather soft conglomerate which allowed the bolt to tip over a bit and it snapped at the bottom. Took 58kN to do it though!
Without a really high quality picture of the end of the bolt who can tell? Get out on one of the dodgy routes with a torque wrench and test a few!
Jim
In reply to jimtitt:
A very interesting topic. I've been contemplating similar (though quite different) in preloaded bolts in steel connections subjected to combined shear and tension. Talking about 1500kN tension and 300kN shear in a statically loaded structure with 8 or more 30mm HSFG bolts, but the theory should be the same.
I've only got limited experience with resin anchors which are notoriously bad at carrying load (when used as a replacement for cast-in concrete bolts), though a hell of alot better than mechanical fix.
I would suspect with a mechanical fix bolt that overtightening will overstress the rock a long time before it reaches the tensile capacity of the bolt (as Chris is suggesting). The kind of areas the mech fix will be bearing on in the rock (to hold the pretension) will be tiny and the local crushing strength will fail long before even 50% of the tensile capacity of the bolt will be reached. Once the pre-tensioning has been lost, the bolt will be free to move slightly and/or rotate, and especially after a period of use will end up bearing at a couple of points along the bolt and putting the bolt in bending when loaded. If you've got a combination of tension, shear and bending it would be possible to make the bolt fail in a fall situation I would have thought.
That said, overstressing a mech fix bolt would be pretty hard by hand without a pretty big wrench (as Jim said). Technically there shouldn't be a problem until the bolt is stressed in tension greater than the preload, unless the rock has already failed in the preloading stage.
All of this is ignoring he possibility of bad materials and corrosion.
Alot of thinking out loud above - I have no experience of bolts in climbing but quite a bit in structural engineering. If anyone has any links to technical reports or studies I'd find them very interesting to look up. Might make the working day a bit more interesting!
I've never climbed sport but my instinct in using bolts in construction is that I would prefer to trust my life to a resin fix rather than mechanical fix bolt.
A very interesting topic. I've been contemplating similar (though quite different) in preloaded bolts in steel connections subjected to combined shear and tension. Talking about 1500kN tension and 300kN shear in a statically loaded structure with 8 or more 30mm HSFG bolts, but the theory should be the same.
I've only got limited experience with resin anchors which are notoriously bad at carrying load (when used as a replacement for cast-in concrete bolts), though a hell of alot better than mechanical fix.
I would suspect with a mechanical fix bolt that overtightening will overstress the rock a long time before it reaches the tensile capacity of the bolt (as Chris is suggesting). The kind of areas the mech fix will be bearing on in the rock (to hold the pretension) will be tiny and the local crushing strength will fail long before even 50% of the tensile capacity of the bolt will be reached. Once the pre-tensioning has been lost, the bolt will be free to move slightly and/or rotate, and especially after a period of use will end up bearing at a couple of points along the bolt and putting the bolt in bending when loaded. If you've got a combination of tension, shear and bending it would be possible to make the bolt fail in a fall situation I would have thought.
That said, overstressing a mech fix bolt would be pretty hard by hand without a pretty big wrench (as Jim said). Technically there shouldn't be a problem until the bolt is stressed in tension greater than the preload, unless the rock has already failed in the preloading stage.
All of this is ignoring he possibility of bad materials and corrosion.
Alot of thinking out loud above - I have no experience of bolts in climbing but quite a bit in structural engineering. If anyone has any links to technical reports or studies I'd find them very interesting to look up. Might make the working day a bit more interesting!
I've never climbed sport but my instinct in using bolts in construction is that I would prefer to trust my life to a resin fix rather than mechanical fix bolt.
In reply to dangermouse101:
Your right about chemical anchors but in case anyone reads this wrongly the problem is continous load where resin creep is a big problem, glue-in climbing anchors aren´t under load so this doesn´t occur.
As you say, rock failure is the other mode for mechanical fasteners. In soft rock the tags that engage the cone gouge through the rock and it fail to tighten up any more, in harder rock the tags deform and usually jam into the body of the bolt stopping it moving. Where the boundary between soft and hard rock is depends, certainly sandstone you get rock failure and granite clip failure so somewhere between! Some bolts have better tags than others as well which helps in the soft stuff, in conglomerate we have pulled bolts which left the clip inside the hole as the sandy matrix just crumbled outwards under pressure
Not the sort of thing we study a lot though, it´s a horrible job installing bolts, overtightening them and then cutting the rock open to see what failed, a few times through a block of granite satisfied my curiousity!
Your right about chemical anchors but in case anyone reads this wrongly the problem is continous load where resin creep is a big problem, glue-in climbing anchors aren´t under load so this doesn´t occur.
As you say, rock failure is the other mode for mechanical fasteners. In soft rock the tags that engage the cone gouge through the rock and it fail to tighten up any more, in harder rock the tags deform and usually jam into the body of the bolt stopping it moving. Where the boundary between soft and hard rock is depends, certainly sandstone you get rock failure and granite clip failure so somewhere between! Some bolts have better tags than others as well which helps in the soft stuff, in conglomerate we have pulled bolts which left the clip inside the hole as the sandy matrix just crumbled outwards under pressure
Not the sort of thing we study a lot though, it´s a horrible job installing bolts, overtightening them and then cutting the rock open to see what failed, a few times through a block of granite satisfied my curiousity!
In reply to all:
Over the last couple of years I've been having Titanium bolts made in China, shipped to Thailand and tested in Sheffield. I've just made a couple of very slight improvements to the design that has been used in Thailand for about 10 years now.
I've been developing routes and placing these bolts in Thailand and supplying them to friends for the last year.
These bolts used with Hilti RE-500 resin are by far the longest lasting bolting solution in my opinion.
Also they are only about a third of the price of the originals sold by Ushba in America.
They are a welded 'P' shape bolt with machined grooves for the resin to get hold of and blasted with Quatz sand to give a nice, slightly rough surface.
If you would like any more information then please feel free to get in touch.
Cheers,
Martin
Over the last couple of years I've been having Titanium bolts made in China, shipped to Thailand and tested in Sheffield. I've just made a couple of very slight improvements to the design that has been used in Thailand for about 10 years now.
I've been developing routes and placing these bolts in Thailand and supplying them to friends for the last year.
These bolts used with Hilti RE-500 resin are by far the longest lasting bolting solution in my opinion.
Also they are only about a third of the price of the originals sold by Ushba in America.
They are a welded 'P' shape bolt with machined grooves for the resin to get hold of and blasted with Quatz sand to give a nice, slightly rough surface.
If you would like any more information then please feel free to get in touch.
Cheers,
Martin
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