Glue-in Bolt Test Results at Muir

[Saxman]

Well, I guess she's just screwed.

[Alan Evil]

Is there some computer savvy person that wants to write a script for this gambling? Techno bookie? Everyone would have to pony up their money and the winners would get a bigger tax write-off.

[dhoyne]

Just as it is obvious that a long fall on dynamic line causes less total force to the top anchor than a 10' fall due to more rope stretch, it is equally obvious that a long fall on dynanic line causes more force than clipping the anchors and lowering off draws.

The difference is, a 10' fall might not be preventable.

[weber]

deleted

[Wes]

Dude, you are funny for sure. I am amused and somewhat honored that would would spend so much time on a post to me.

Just how many intentional whips do you think are happening out there? It isn't all that many, in fact I would say the number is trivial and statistically irrelevant compared to the overall numbers of "normal" falls. I am no engineer, or alpine climber and I haven't been climbing all that long, but I have seen thousands of falls, and if 10 or less "extra" per 1,000 cause an anchor to fail, then we should all be dead by now. Go to the lode one day during the season and count the number of falls that happen.

You have a personal grudge against something that really is a non issue, and I think you are the irresponsible one. Why not start a crusade against something that might actually be dangerous, like not stick clipping the first bolt.

[weber]

I love what Rick is doing and can't wait to see the data. To make things interesting, and no offense to Rick, I will bet $25 that the long whipper will have a lower peak force than the short fall. The money will of course go to the coaltion. As a fund raiser, more people should bet as well. Why not have some friendly fun, raise money, and enjoy some geeky science all at the same time? Anyone else want to put their money where their mouth is?

An important point here that many of you seem to be missing is that a VW, unlike a typical lead climber fall, is a deliberate and totally unnecessary stress on bolted hardware. Increasing risk to those who follow us on routes, whether we VW or wear out the anchors by lowering through them, is irresponsible.

Wagering on force comparisons here is silly. Short falls on short lengths of rope will most likely produce higher peak impulse forces than long falls on long lengths of rope. So the hell what?

Some of you non-engineering types might want to look into cyclic loading.

Rick

[weber]

Dude, you are funny for sure. I am amused and somewhat honored that would would spend so much time on a post to me... You have a personal grudge against something that really is a non issue...

My post was directed to you and everyone else who takes VWs. No personal grudge. I, and a hell of a lot of reputable, experienced climbers, gear manufacturers and engineers, simply believe you folks are irresponsible. Period.

Rick
_________________
When I disagree with a rational man, I
let reality be our final arbiter; if I am
right, he will learn; if I am wrong, I will;
one of us will win, but both will profit.
-Ayn Rand

[Wes]

Cool with me. I think you all are wrong, and have 15 years of sport climbing in the red and tens (hunderds?) of thouands and counting falls on my side of the coin. Not to say that bolts won't start failing left and right, but the worst ones I have seen when being repaced has much more to do with whether or not the bolt stays dry, not how many falls it has caught.

[weber]

Cool with me. I think you all are wrong, and have 15 years of sport climbing in the red and tens (hunderds?) of thouands and counting falls on my side of the coin. Not to say that bolts won't start failing left and right, but the worst ones I have seen when being repaced has much more to do with whether or not the bolt stays dry, not how many falls it has caught.

Cool with me too. We agree to disagree. One of many things I DO respect about you, Wes, is your post a few months ago agreeing to follow MV's policy on no VWs. Thanks.

Rick

[Wes]

No worries, I fully support you and your decisions on what you think is best at Muir, and I have yet to break any of the rules there, and have no plans / desire to do so. I think it is hella cool what you have done there, so even if I am a pain here and over this issue, I do have plenty of respect for you, Liz, and all of team Muir.

Wes

[tomdarch]

Oy vey! In an ideal world, this hijacking would be moved to the original 'VW' thread.

But it does raise an imporant point: cyclic or repeated loading. As much as I understand it, there is a threshold of force for steel, at least, below which repeated loading just doesn't matter. (You start talking about it taking millions or more repetitions to get any weakening or failure, where with bolts we're talking about thousands of repetitions making a difference)

What might be the worst case scenario for a given bolt? Let's say that it's the most popular route in the world, people climb it non-stop 10 hours a day and fall an average of once every 10 minutes over the course of the day. That's 60 falls a day, 365 days a year = ~22k falls a year. This is a fairly absurd scenario outside of a gym, but it does mean that a bolt could potentially see falls numbering in the hundreds of thousands over the course of 10 or 15 years.

But realisticaly, you need to plan on something in the range of tens of thousands of falls on a bolt during it's lifetime. Most will never see this many, but a few will.

So, between the bolt, potentially the glue, and the rock, these all need to withstand some tens of thousands of loadings. I wouldn't be as confident as Jim that cyclic loading isn't a concern.

Does anyone know if Hilti has done much cyclic testing on their 'glues'? There's a bunch of different stuff out on the web, but a lot of it is either seismic (high loads, few cycles) or bridge (relatively low loads, many, many cycles) related.

[dhoyne]

In soft and friable rock this would, over time, result in elongation of the holes as well as undue amounts of stress on the bolts themselves.

It's not the bolts failing that I'm really worried about in this particular instance. The bolts are probably stronger than the surrounding rock. The cyclic loading on the rock will damage it each and every fall... eventually opening a fracture which will lead to a failure of the bolt/rock system.

I'm very anxious to get some rock plugs to throw onto my Tinius Olson tensile / compression testing machine at work. I have a striking feeling that while steel can endure many impacts under its compressive yield point with little long term affect, the yield point in Corbin sandstone is so low that each and every impact causes a small amount of damage. Steel and heat treated aluminum alloys have pretty good
ductility, meaning there is a range between the yield point and breaking point (UTS, or ultimate tensile strength). Rock, like ceramics in general, do not. They are VERY brittle. Rock doesn't bend when loaded, it breaks.


---and yes, my degree is in Materials Science Engineering, with a specialty in ceramics (rock can somewhat be classified as a ceramic material based on characteristics and properties)


My general feeling -- why purposely put stress on equipment that many other people are using? So what if it doesn't fail when you use it; you're contributing to the failure of the system. It may be in a small way, like any other fall. But the point is, you're putting unneccesary loading on the system. A system that many people believe (however untruthfully) to be foolproof.

[the lurkist]

what a good discussion.
Dhoyne- In your opinion (noted that, as you stated, you haven't test Corbin SS, yet) would rock, Corbin SS, be prone to fracture and possibly ultimately fail secondary to cyclic loading if no movement was introduced between the bolt and the stone, i.e. the bolt was immovable in the hole?
Thanks

[weber]

Yeah, Dave, I'm looking forward to those tests too. I'll get you some rock hunks soon.

Cyclic loading:

More than metal fatigue, here is what is concerns me most. Let's take a real world example -- the last bolt before the top anchors on Cherry Red. This route has been closed since last fall until the mechanical bolts are replaced with glue-ins. A few days ago, we removed this bolt and the hanger.

This particular bolt was in a hole that was drilled such that the outer diameter was a little larger than it should have been. Ideally, a half inch drill will make a half-inch hole. In reality, it is impossible to hand hold a hammer drill and get a half inch hole. Really skilled drillers, like Karla and Jared, are able to keep the augering out to a minimum, but the outside of a well-drilled hole will always be at least a few thousandths larger than the inside. A tightly-drilled hole like this rarely has a loosening problem. The bolt goes in tight and stays tight for a long time.

Unfortunately, the hole on Cherry Red is in a severely overhung hard-to-drill section of rock. And, the route developer (or perhaps another person he had do the drilling) inadvertently opened the outside of the hole to perhaps 5/8 inch dia.

Here is why this is problematic. Although the cone is snug in its little 1/2-inch diameter section of the hole and the bolt is properly tightened, the outer portion of the bolt, just under the head can be infinitesimally deflected up and down as it is subjected to repeated falls. The sandstone simply crushes a tiny bit with each "cycle" until the hanger works free, and ultimately, the cone, being rocked a little each cycle, works free. Now, you have a potential for a blown bolt.

Remember, I said a well-drilled hole rarely has a loosening problem. But, even in a few properly-drilled placements that receive many loading cycles, the outer end of the bolt could flex up and down a tiny bit, each time crushing a smidgen of rock. The more the hole opens, the more the bolt can flex. Eventually, a failure could occur. This is one good reason for using glue-ins, wherein not even the tiniest bit of play exists after they are installed.

Rick

[Horatio Felacio]

i don't really see the point in testing the rock? there are so many variables involved at each crag in the gorge, and even each climb.