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Chockstone Forum - Accidents & Injuries

Report Accidents and Injuries

 Page 1 of 2. Messages 1 to 20 | 21 to 30
Author
Rockfall resulting in chopped anchor report

Miguel75
24-Feb-2015
6:39:42 AM
Here's an interesting account of an accident resulting in minor injuries that could have been much worse;

http://mountainproject.com/v/rock-fall-results-in-chopped-anchor/110088639

IdratherbeclimbingM9
24-Feb-2015
9:21:51 AM
Thanks for that link M75.
It is a good write up and I think they were blerrie lucky that the outcome wasn't worse.

Good thoughts were expressed in it also about the vulnerability of a magic-(sliding)X in that situation, due to often no redundancy being involved...

Macciza
24-Feb-2015
11:10:02 AM
One should always tie off the arms of a sliding-x to avoid extension...

sbm
24-Feb-2015
11:43:20 AM
"The leader had moved through the "double cracks" when a LARGE block fell. (I think the piece in the middle, between the cracks, decided it was time to go). After free falling for about 30' it landed in the gulley about 20' above us and exploded into 3 or so microwave size blocks, a bunch of shrapnel and blasted through us and the belay... I tried to jump and dodge (Matrix style) the barrage of granite. ...
I was less than successful, got blasted full force in the legs below the knees and ended up below the anchor, in the corner, on my back with a block on my chest/stomach"

Whoa! I think their anchor equalisation decisions were the least of their problems.

IdratherbeclimbingM9
24-Feb-2015
12:00:45 PM
On 24/02/2015 Macciza wrote:
>One should always tie off the arms of a sliding-x to avoid extension...

... & in this case avoid total belay failure due a cut sling connected to two bolts.

In this case it had been tied off, and when one side was cut/failed two people were left hanging off the remaining strand instead of going the way of the rock, had it not been so.
kieranl
24-Feb-2015
2:20:14 PM
Now I don't like the sliding-X but it appears that people are missing the main lesson from this event.

The lesson is that if you're caught in a big rockfall it is purely a matter of luck whether you will survive or not, so be really careful with that stuff. Yes rig your belay properly and clip your rope into redundant anchors but big rocks will chop anything if they hit. If any of the non-redundant bits like the powerpoint knot, or the rope to each climber had been chopped then it would be goodbye.

martym
24-Feb-2015
10:48:50 PM
There's a video with Alex Honnold (I think AFJ posted?) where a guy is leading, there's some rockfall and he continues to lead, belayer just keeps paying out rope.. Leader builds anchor, hauls up rope... Then screams.
The rope had been completely severed and neither noticed.

shortman
25-Feb-2015
6:28:45 AM
Ring a bell Andrew?

ajfclark
25-Feb-2015
7:27:30 AM
Nope.
martym
25-Feb-2015
8:05:18 AM
It was a talk with Alex and a photographer (I think he was hosting it?) they'd been climbing with an old legend somewhere like Greece or Turkey something... Mostly photos... Alex then remarked how much more dangerous that situation was than solo climbjbg because they had the false assumption the climber was protected.

ajfclark
25-Feb-2015
8:13:49 AM
Perhaps it was the Croft/Honnold talk about Risk and Reward?

http://www.chockstone.org/Forum/Forum.asp?Action=Display&ForumID=4&MessageID=3094&Replies=7
martym
25-Feb-2015
8:51:39 AM
Sounds right.

So regardless of personal preference, is there any actual advantage of the tied off vs sliding x on two redundant knots? Presumably when one leg failed, the anchor still slid some distance to fully weight the only remaining bolt?
In this case there was only one (albeit large) knot - one potential point f failure:



While in the sliding X you have two redundant knots, but slightly more extension:
Dave_S
25-Feb-2015
9:08:00 AM
The sliding-X with limiter knots still has no redundancy between the limiter knots, and the limiter knots are also not redundant, as if one fails then the whole anchor fails, whereas when tying a sling like a cordelette, you would need to cut a minimum of two strands in the master knot in order to cause failure, so it is somewhat redundant.

Also, DMM drop tests suggest that when tied in Dyneema, a sliging X with limiter knots could fail in a FF1 fall (on a static tether, not on a climbing rope). They didn't exactly test the X with limiter knots, but the "overhand knots" configuration that they tested could be thought of as equivalent to one, except that in the X if one knot fails then the whole anchor fails.

ajfclark
25-Feb-2015
9:14:34 AM
If the statically equalised anchor was properly weighted before the leg was cut, there'd be no extension, just a swing.

That said, in this instance with the guy likely diving to the side I doubt both legs were equally tensioned so there is a possibility of some extension as the slack was taken up if the tight side was the one cut.

If he went right, the right leg would've built up slack, then as the left leg was cut there would've been a slight extension as the slack got taken up.

If he went left, the left leg would've been slack and there'd be no extension.

With a sliding x, if he didn't move far enough to be against a stopper knot, there would be extension either way. If he was against a stopper knot, the situation is similar to the above depending on which way he went.

Given there was also climbing rope in the system, it should've absorbed most of any impact.



re: the redundancy of the powerpoint: you only need cut one strand of the powerpoint in a sliding x for it to fail vs 2 in the statically equalised sling and I think the powerpoint knot would also hold up to more abuse than the sliding x limiter overhands.
kieranl
25-Feb-2015
9:23:27 AM
I'm utterly bemused by the way this thread keeps coming back to talking about the sliding-X, which wasn't even a feature of the incident.

If you're planning your belay rigging to allow for the possibility that your belay is going to get chopped by rockfall then you've got bigger issues than whether to use a powerpoint knot or a sliding X with limiter knots.

ajfclark
25-Feb-2015
9:34:01 AM
On 25/02/2015 kieranl wrote:
>I'm utterly bemused by the way this thread keeps coming back to talking about the sliding-X, which wasn't even a feature of the incident.

Why?

The thread is about an anchor partially failing because a leg was cut and so it seems reasonable that the discussion has moved to what happens to anchors when a leg is cut. Sliding x probably gets more air time because it does more in the same situation.
kieranl
25-Feb-2015
10:11:01 AM
On 25/02/2015 ajfclark wrote:
>On 25/02/2015 kieranl wrote:
>>I'm utterly bemused by the way this thread keeps coming back to talking
>about the sliding-X, which wasn't even a feature of the incident.
>
>Why?
>
>The thread is about an anchor partially failing because a leg was cut
>and so it seems reasonable that the discussion has moved to what happens
>to anchors when a leg is cut. Sliding x probably gets more air time because
>it does more in the same situation.

That's where I think it's being misinterpreted, confusing cause and effect. The cause of the incident was that the anchor was exposed to rockfall, it wasn't that a leg of the anchor was cut.

So, the important question, as I see it, is how do we avoid a belay being compromised by rockfall? That's a harder question because it's not as simple as deciding which tie-in method to use - it's about being able to evaluate the situation, exercising judgement and then controlling what variables you can.
stuart h
25-Feb-2015
10:30:46 AM
I'm with Kieran on this question. The first thing that strikes me about this accident & suggests what lessons might be important in avoiding a similar, very probably worse outcome in future, is that the belay is exposed to rockfall. The description on the mountain project thread refers to it being in a corner/gully or something like that. One of the hangers had already damaged by rockfall when they arrived. It doesn't seem like a great place to establish a belay & even though someone drilled there, the fact that another belay station had been built on the arête/edge of the gully really seems the more important thing here in terms of the key take away lesson from the incident. It is a dramatic illustration that if they had anchored using a sliding-x without limiting knots the cutting of the sling at that point would have lead to complete anchor failure whereas the tied-off sling featured redundancy that kept the belayers anchored, but that redundancy could be achieved multiple ways and none of these questions about how you connect to the anchor seem, particularly in this case, anywhere near as pertinent, especially in terms of how people are likely to be killed climbing, as the question of where you position that anchor/yourself.

Unlucky that it sounds like they had spontaneous rockfall, but, once it is in motion, a really lucky outcome for these guys, thankfully.
Dave_S
25-Feb-2015
10:33:33 AM
Sorry, correction to my previous post - cutting one strand of a limited sliding X in between the limiter knots does not cause total failure, however a failure of one of the knots still will. (This is what happens when I post to Chockstone immediately after getting out of bed. I'll assume ajfclark had also just gotten out of bed.)

ajfclark
25-Feb-2015
10:46:01 AM
Either that or I should've got some string and played with the setup.

After playing with some string, cutting either strand near the carabiner is bad and releases the carabiner if some other part of the sling outside the limiting knots failed or either piece. so still two pieces of sling need to be damaged.

I think even damage near the limiting knots could be very bad. If it were very close, it'd be like a EDK with very short tails.

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There are 30 messages in this topic.

 

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