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Bolt/Bolting failure Sanddrif

Posted: Mon Sep 14, 2009 6:01 pm
by zabullet
On Thursday 10 September, there was a bolt/bolting failure at the Sanddrif Sports crag, Cederberg.

I'll provide as much of this post as facts alone and leave the speculation, flaming, etc up to the rest of the forum goons.

It was the 3rd bolt of "Lip Service". The bolt was in a roof and had previously been rested on, but during a minor fall (30cm above bolt) it pulled, inverting the climber, who was then arrested by the second bolt. There was minor injury to the climbers lower back (although I suspected major mangina trauma at the time).

It should be noted that the bolt showed a very small amount of oxidization and the threaded part stuck prominently out from the hanger (making it tricky to clip a quickdraw).

On a side note; there's a biner on the second bolt if anyone wants to return it to me.

zb.

Re: Bolt/Bolting failure Sanddrif

Posted: Mon Sep 14, 2009 6:57 pm
by justin
Thanks for the report.
Q's: Did the failed bolt have a 'C' on the end?
Do you still have the bolt? (ARF will want to have a look at it & perhaps the manufacturer)

Hope the climber is ok!

Re: Bolt/Bolting failure Sanddrif

Posted: Mon Sep 14, 2009 8:38 pm
by zabullet
Justin wrote:Q's: Did the failed bolt have a 'C' on the end?
No it did not (as far as I can tell). It's a fairly new bolt and hanger (think the route was bolted 2004/2005,certainly after 2000).
Justin wrote:Do you still have the bolt? (ARF will want to have a look at it & perhaps the manufacturer)
I do have the bolt and ARF are more than welcome to inspect it to see if they can learn anything. I would like it back however as I plan on framing it for the climber as a momento.

As the bolt didn't sheer (just pulled out) I think it makes it a relatively unusual failure from what we normally see in the WC (correct me if I'm wrong). However, I think we can learn something from it.
Justin wrote:Hope the climber is ok!
It seems that way. Just a bash, so appears it is just stiff from bruising.

zb.

Re: Bolt/Bolting failure Sanddrif

Posted: Tue Sep 15, 2009 7:37 am
by Russell Warren
In the Cederberg rock which is normally fairly hard one gets patches of soft rock. When you are drilling the holes you can actually feel the differrence in the rate that the drill goes in. The thing that complicates this is that sometimes the crust of the rock is hard and the core is soft, but in all cases you will find that the bolt does not set properly i.e. you will not be able to reach the 30 N.m. required to set the express anchors and the nut will keep turning. If this happens one needs to remove the bolt, drill a 12mm hole and put a glue in bolt in place. This is the only way of ensuring safety in that type of rock. Andy Davies can problably elaborate on what I have said here. The Sandrif situation is worse as the bolt sounds like it was entirely in tension and therefore had no "side support". From my experience most bolts, even those place in the softer sand stone if placed perpendicular to the vertical have little chance of pulling out, but a glue in should still be used instead.

Re: Bolt/Bolting failure Sanddrif

Posted: Tue Sep 15, 2009 8:09 am
by Andy Davies
Russell is entirely correct - the Cederberg does have a lot of soft sandy rock. I replaced a few dodgy bolts at Truitjieskraal and when bolting Adultworld I pulled some bolts out with body weight. I had to use 120mm long glue-ins. ARF will replace the bolt at Sandrift with a glue in when one of us gets out there. Please note that when you bolt a route you take on a lot of responsibility and you need to think carefully about all your bolt placements. An example is: ARF has specified 90mm anchors to prevent this sort of thing happening so please refrain from using 70mm anchors.

If you suspect any problems, please feel free to contact me through the MCSA CT.

Re: Bolt/Bolting failure Sanddrif

Posted: Tue Sep 15, 2009 6:04 pm
by Marshall1
How do longer bolts prevent this from happening? Rock is not nessesarily harder inside.

Re: Bolt/Bolting failure Sanddrif

Posted: Wed Sep 16, 2009 1:16 pm
by Russell Warren
In my opinion it would increase the size of the failure cone if the rock was to fail and does not relate directly to the bolt pulling out in tension. I don't think it would make much differrence to that scenario.

Re: Bolt/Bolting failure Sanddrif

Posted: Wed Sep 16, 2009 4:01 pm
by Russell Warren
I believe that ARF rule of using a longer bolt is good one for the bolting of new lines especially when one takes into account the variance in experience levels of people out there bolting. The margin for error with a longer bolt is higher as you have a larger "failure cone" resisting any weaknesses in the rock that you may not see.

Re: Bolt/Bolting failure Sanddrif

Posted: Wed Sep 16, 2009 4:59 pm
by shorti
Here's a picture of the bolt that came out. I fell on it shortly after the pic was taken (earlier this year) :pale:

Image

Re: Bolt/Bolting failure Sanddrif

Posted: Wed Sep 16, 2009 6:26 pm
by justin
Funny... you're taller than I expected :)

Possibly put that 3rd bolt on the lip of the overhang?

Re: Bolt/Bolting failure Sanddrif

Posted: Wed Sep 16, 2009 8:06 pm
by mokganjetsi
tall? shorti has the wingspan of a pterodactyl! he clipped bolt 4 from that same spot when he sent the route......

i wondered about the sense of putting the bolt there - aligned with the direction of the force generated by a fall. if the fall direction and bolt are at 90 degree angles then even a fairly loose bolt should stay in place

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 17, 2009 8:43 am
by peanut
Great place to put a bolt! That things gonna come out no matter how solid the rock is!

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 17, 2009 8:56 am
by emile
Love the caption on the front page pic
Follow the bolt tha failed
...... Metallica baby, yeah!! :mrgreen: 8)

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 17, 2009 9:17 am
by justin
peanut wrote:Great place to put a bolt! That things gonna come out no matter how solid the rock is!
You're joking right :? Bolts placed in a roof like that are very common (and hold no problem)

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 17, 2009 9:27 am
by peanut
mokganjetsi wrote: i wondered about the sense of putting the bolt there - aligned with the direction of the force generated by a fall. if the fall direction and bolt are at 90 degree angles then even a fairly loose bolt should stay in place
I have to agree with Mok... 30cm up above the lip is probably better, but hey, I havent done the route, so ....

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 17, 2009 10:06 am
by Russell Warren
@Peanut. Have you ever placed an expansion bolt. In solid rock it is hardly necesary to torque the bolt. Once you have hammerred the bolt into the hole you have more chance of falling pregnant than pulling it out again. A bolt in a roof has to be placed like that so the bolt in tension is not a problem per se, but in this case the rock is. That said I do not see any disadvantage of placing the bolt on the lip as Justin suggested.

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 17, 2009 10:26 am
by mokganjetsi
having the bolt below the roof makes for convenient clipping - that warm fuzzy feeling when you pull up into-and-over the lip....... i have seen a few routes where you there's a bolt in the roof and then another one just above the lip (like 50cm apart) - maybe overkill but definitely less sweating on the leadout.

anyways, hope the route gets fixed soon - its one of the best 22s in SA

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 17, 2009 10:30 am
by peanut
Yip, have placed bolts, both expansion and glue ins.
So, the bolt pulled out the hole, right? A chunk of rock didn't come out with the bolt?
The bolt failed, not the rock holding the bolt?
Although it may be cool to place bolts like that, and often there are no other alternatives,
surely you have a stronger placement when the bolt is at 90 degrees to the direction of the fall.
Like 20- 30 cm above?
I'm not criticizing the way it was bolted. I just think its not surprising that the thing pulled over time...

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 17, 2009 10:50 am
by pillick
I always thought Shorti was a hardcore chick - no i see that he is just a guy... bummer....

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 17, 2009 11:02 am
by Ray
I would argue the following: if the bolt pulled out, it could be that the hole drilled was larger than the recommended/specified diameter for the anchor. ie, if the rock is fairly soft, when drilling, the hole becomes larger than was necessary. On top of this, it is possible that the anchor wasn't tightened enough, (although a look at the anchor would help). If it was a cone failure - the whole chunk/cone of rock would come out.

It seems to me that this is a bolting issue. The failure loads of these bolts (shear or tension) are unlikely to be the cause of the failure, in my opinion anyway. I agree that in this case, chemical anchor bolts would be better.

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 17, 2009 11:34 am
by shorti
BOLS! I clipped the 4th from higher!

I agree that it will be a stronger anchor over the lip, but it might be a little hard to clip. The last good foot hold is well below the 2nd bolt. So a bolt over the lip will have to be clipped from a lock off on the good jug with essentially nothing for the feet. I'm no chick (its sad but true), but I am hardcore (haha) enough to not want a warm fuzzy bolt ladder, the 4th bolt is right there. I'm no expert with bolts either, but I think maybe it came out because you can't really take a proper fall on it, its more of a swing. A rather violent one too, because the rope out it so short. Short jerky swings like that on trad gear for instance will have a fair chance in pulling them out, so maybe the same happens over time with the bolt - soft rock, lots of short and hard pulls from side to side. Ok, that's probably rubbish...

1Dog, I take exception to you insinuating that I listen to these so called rock and roll orchestras. Mama said they are from the devil! :clown:

Pillick you have thoroughly disturbed me there man, if I was a chick I would have been a thing that should rather not have been :mrgreen:

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 17, 2009 11:39 am
by Russell Warren
No argument from me Peanut, 90 degrees to the force is better, but the fact remains that in solid rock the anchor will never slip out (if the hole is the correct size i.e. you have to use a hammer to get the bolt into the hole) not even over an extended period of time. In this case the rock was soft so there was not a cone failure, but the hole effectively becomes too big and the bolt just slips out. I have pulled bolts out by hand that have been placed on soft rock.

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 17, 2009 12:01 pm
by peanut
Agreed! Bolts in solid rock are more than likely bomber.
Its just sensible to eliminate any variables when placing bolts, if one has options.

Re: Bolt/Bolting failure Sanddrif

Posted: Mon Sep 21, 2009 2:05 pm
by DaveD
FYI
In the Blue Mountains (Australia) they only place glue in's for this exact reason. The rock is a soft sandstone and expansion bolts are not secure enough.

Re: Bolt/Bolting failure Sanddrif

Posted: Mon Sep 21, 2009 2:43 pm
by mokganjetsi
oh yeah, sorry shorts - reviewd the pics and saw you clipped from the rail. about 15cm runout from the bolt...... i'm also glad you're not a girl. imagine those hobbit feet on a girl yikes!! :)

Re: Bolt/Bolting failure Sanddrif

Posted: Thu Sep 24, 2009 3:37 pm
by paddy
Not sure I wanted to regenerate this thread as I feel very embarrassed (and also very shaken) by the bolt failure. However, I thought it important from a learning perspective to set out the thinking and circumstances of the bolt placement. But first off my apologies to the guy who experienced the bolt failure - I'm just really glad there was no serious injury.

Firstly the location of the bolt. The earlier picture tells it all. Without writing a book on the topic, given the circumstances, that was the bolt placement to protect the crux.

From the perspective of placing a bolt in the direction of the fall - my understanding of the mechanics/physics of an expansion bolt placed in this way (assuming adequate rock quality) is that the holding strength of the bolt should be bomber.

Regarding the rock quality. Nothing about this placement suggested that there were problems with the rock. The rock sounded solid when tapped with a hammer, the bolt gripped without any slippage, the general rock quality of Sandrif is excellent (definitely a step ahead of the Truitjies).

So what happened. It would be interesting to hear if the hanger was spinning at the time of failure as this could indicate that the failure was progressive as opposed to being sudden (not sure if this makes a difference at the end of the day). My speculation is that rock quality is the likely problem. My theory is that the rock was initially good enough, but nonetheless was soft enough to wear away with repeated loading. An alternative could be the type of expansion bolt used for the placement. I think I might have used the type with 2 narrow expansion sleeves (as opposed to one long expansion sleeve). It could be that only one sleeve took ( I assume this compromises holding strength).

So what to do. While I don't think bolting practices in the Blue Mountains is a relevant reference point as the rock type is very different (it is essentially mud with a patina covering), I doubt a glued in bolt would have pulled. This does suggest that perhaps glue-ins should become the standard as this should largely discount rock quality as a variable. It also has other benefits.

ps the reason there was more thread exposed on this placement is that this was deliberate due to the orientation of the bolt.

Re: Bolt/Bolting failure Sanddrif

Posted: Fri Sep 25, 2009 7:54 am
by zabullet
Hi Paddy,

Thanks for the concern, its appreciated.
paddy wrote:It would be interesting to hear if the hanger was spinning at the time of failure
To my knowledge, no.
paddy wrote:the reason there was more thread exposed on this placement is that this was deliberate due to the orientation of the bolt.
My thought was that perhaps it was a gradual failure and that the hanger had previously been spinning, but the nut re-tightened, accounting for the "excess" of exposed thread.
paddy wrote:I think I might have used the type with 2 narrow expansion sleeves
It is. I'll try and get a photo up this weekend of the bolt. I my layman's inspection, it appears that both sleeves "took".

....on a side note, this failure got me thinking about bolting practices. I personally haven't bolted, so I'm sure there are lots of caveats to what I'm about to suggest, but I going to put this out there.

There are several climbs (not this one), where easier sections of the climb up to a crux are scarcely bolted and then the crux is protected with a single bolt. My concern is that having a largish run-out just before a crux with a single piece of protection that is likely to be hammered over time is going to lead to a larger than necessary fall if that bolt blows or pulls.

It seems protecting a route comes down to "what are the chances someone is going to fall here", perhaps one should sometimes ask "what happens if the bolt above this fails, am I creating several meters of slack"

....just some thoughts. Flame away.

zb.

Re: Bolt/Bolting failure Sanddrif

Posted: Sat Sep 26, 2009 10:12 am
by XMod
This thread has said it all already so adding my 2c seems a little arbitrary, but I cant understand why Patrick would have chosen to expose more thread regardless of the bolt orientation. All mechanicals must always be placed to the full depth possible, the shallower you place the bolt, the less rock that gets engaged and the weaker the placement (It always the rock that will fail not the bolt (SCC aside), so looking at specs handed out by bolt manufacturers is a bit pointless really). This is especially true of the old UPAT double sleeve bolts (now not used anymore) as the lower sleeve is only a few mm from the thread.

ZB doesnt state what the hole looked like after the failure, was a conical hole left behind (indicating rock failure) or was the hole still more or less the same size and round (indicating soft rock which allowed the bolt to simply slide out)?? Repetitive tightening of a bolt in soft rock can also cause a lot of thread to be exposed.

Unfortunately its not always possible when drilling to know if the rock is too soft, high powered drills fly into the rock making it hard to judge if youve hit a soft spot. Always thouroughly brush and blow the hole out and inspect the walls of the hole (use a torch to see inside if necessary), if they are smooth round and regular the rock is probably hard, if parts of the hole wall have broken out and the hole looks rough and irregular youve hit soft rock and should place a glue-in bolt. Always place 90mm bolts under rooves and at cruxes. If you think a placement needs a glue in dont slap a mechanical in just so you can start playing on your new toy straight away (even if it is many miles from home) rather get it checked out by an experienced route opener and put in the correct bolt (glue-in if required). To do otherwise is to create a time bomb that may kill someone in the future - not cool!!

Other ppl have also placed bolts like this (thread exposed) during the early days so watch out for placements that look like this as they are usually dodgey. That said Patrick bolted the route well, there are two bolts close to each other below the crux which is exactly how things should be. Runouts are ok provided youve got at least two bolts below them, the lower of which should still be at a height to keep ur ass off the deck (always include run out length, rope slack, leg length and rope stretch when calculating fall distances - premark propsed placements on toprope and sus everything thoroughly from the ground before drilling). The two bolts close to each other saved the climbers life in this incident.

Re: Bolt/Bolting failure Sanddrif

Posted: Sat Sep 26, 2009 11:13 am
by Stu
XMod wrote:Always place 90mm bolts under rooves and at cruxes. If you think a placement needs a glue in dont slap a mechanical in just so you can start playing on your new toy straight away (even if it is many miles from home) rather get it checked out by an experienced route opener and put in the correct bolt (glue-in if required). To do otherwise is to create a time bomb that may kill someone in the future - not cool!!
So where do we go to get glue-in's, and what do we need to place them (apart from the drill and bit)?
I only need one, so does that mean I have to buy a whole container of glue for just one bolt?

I hit what I believe to be a softer piece of rock (Paarl Rocks), but is by no means weak or crumbling, so instead of placing a standard 90mm I continued to drill until the rock once again became hard - at about 130mm - and so was going to find a 150mm bolt and place that instead.

Any thoughts?

Re: Bolt/Bolting failure Sanddrif

Posted: Sat Sep 26, 2009 1:33 pm
by XMod
Putting in a longer mechanical may still not necessarily make a sound placement.

For glue ins I think you would need to speak to Andy or ARF as ARF seems to have bought all the Raumer bolts in Cape Town! Whilst City Rock has another make of glue in in stock, they have a short shaft. You should probably use the longer length bolts to make sure youre anchoring into solid rock deep in your hole. Get someone who has done this before to come set the bolt for you (ARF personell) they will also have access to equipment (blowers, brushes, glue guns and glue cartridges), you would probably need to co-ordinate it with them so you get to use some leftover glue from another job before it goes off. Maybe when they do Waterfront if that hasnt happened yet. I am also ARF and have a glue gun for Hilti glue (we would still need to access the other stuff) so if u stuck give me a shout. ARF might not be keen on fixing new routes(?), if not I have to some work out at Hellfire so maybe you can piggy back on that and use up my glue if there is leftover.

If the outer rock is supect is it not worth simply drilling another hole? Then patching over the old one. Not the prettiest solution but simpler. What you decide will depend on the rock around the suspect hole, if it all looks similar then a glue in is the best bet.