Loose resin anchors

[Bob Mehew]

There is no system of routine inspection in the BCA anchor policy; instead it makes you the inspector of your anchors.

There was a system for inspecting anchors up until some 5 to 10 years ago.  We stopped it because:

a) we concentrated on providing the anchors could match the mountaineering anchor standard (BS EN 959:1997 subsequently superseded by the 2007 version) which did not require routine inspection by inspectors, only inspecting by users; and

b) the program of inspecting over 5000 anchors was consuming considerable effort by the installers for little benefit.

Please closely inspect all anchors. Do not overlook even the slightest movement. If there is any discernible movement then it is a loose anchor and needs to be reported. We need to know about loose anchors because we need to find out the scale of the problem and if it is a growing problem.

There is a problem with using the phrase "slightest movement" as we used to experience reports of movement which when checked were wrong.  We eventually put it down to people mixing up movement of the anchor for flexing of their fingers.  Simon has quoted the BCA Anchor Policy statement, not the user guide, see http://british-caving.org.uk/wiki3/doku.php?id=equipment_techniques:safe_use_of_eco_anchors.  That states "Twist the anchor using the fingers, while observing any movement. Slight flexing or rotational movement (+/-1mm) of the anchor is acceptable."  The 1mm allowance is to allow for people to mixing up finger flexing for actual movement.  Some work carried out by CNCC Tech Group in 1994 indicated that a properly placed anchor would flex some 0,06mm under a 85kg load.   

 

[Madness]

"Twist the anchor using the fingers, while observing any movement. Slight flexing or rotational movement (+/-1mm) of the anchor is acceptable."  The 1mm allowance is to allow for people to mixing up finger flexing for actual movement.  Some work carried out by CNCC Tech Group in 1994 indicated that a properly placed anchor would flex some 0,06mm under a 85kg load. 

Surely you need to differentiate between flex and rotation. A certain amount of flex when loaded may not be a problem, but rotation however small means the resin bond has failed. Failed resin means weaker anchor. I seriously doubt anyone could cause an anchor to flex using just their fingers.

 

[Simon Wilson]

I had already thought about what Bob says and I decided to treat people as being intelligent. I think the advice that "Slight flexing or rotational movement (+/-1mm) of the anchor is acceptable." is not good advice. If there really is rotation of 1mm then the anchor is loose. In fact if there is any visible rotation then the anchor is loose. The anchor needs to be firmly in place with no movement.

I have never been told of a loose anchor and then discovered that there was no loose anchor. If that was to start happening then I would deal with it. I have no intention of going out inspecting loose anchors because I don't have time. I don't feel obliged do anything about replacing loose anchors but I want to encourage people to report them because I think we need the information to assess how big the problem is.

 

[ianball11]

Big difference between 0.06mm* and 1mm  and I doubt I could apply 85kgs of force with my fingers.

As a bca cim, any chance I could have one of the anchors you pulled out of Heron please Simon/Graham?

Any luck tracking down the installation date etc of the Heron anchors from the cncc tg?  If there were others who would be willing to give a suspect anchor a visit then similar aged installations would be a good starting place?


*Does properly placed suggest that you wonder if these anchors with 3mm movement may have been improperly placed Bob as suggested earlier?

 

[Simon Wilson]

Big difference between 0.06mm* and 1mm  and I doubt I could apply 85kgs of force with my fingers.

As a bca cim, any chance I could have one of the anchors you pulled out of Heron please Simon/Graham?

Any luck tracking down the installation date etc of the Heron anchors from the cncc tg?  If there were others who would be willing to give a suspect anchor a visit then similar aged installations would be a good starting place?


*Does properly placed suggest that you wonder if these anchors with 3mm movement may have been improperly placed Bob as suggested earlier?

The removed anchors are the property of the BCA and I feel obliged to take them to the next E&T Committee meeting. If you are genuinely interested PM me.

I think the anchors might be coming loose because the resin is shrinking but we need as much data as possible to help us find out which is why have appealed for reports.

 

[owd git]

I apologise. I might have been assuming people understand more about the bonding of anchors than they actually do.

If the resin plug was detached from the rock and wobbling about in the hole, I think it is safe to assume that the extraction force would be significantly reduced.

I had already thought about what Bob says and I decided to treat people as being intelligent. I think the advice that "Slight flexing or rotational movement (+/-1mm) of the anchor is acceptable." is not good advice.

I have never been told of a loose anchor and then discovered that there was no loose anchor. If that was to start happening then I would deal with it.

pleaseP.M. me with an explaination as to how these are reasonable postings Simon. you are 'king rude with no founding in science. If this bans me 'so be it'
O.G.

 

[Bob Smith]

I too am confused by the term rotational movement, then a linear dimension given to quantify this. Whilst I would agree that trying to express this to the layman in words alone may be problematic, perhaps a diagram could clear up any misunderstandings.

As a complete aside It would be interesting (but by no means a certainty of safety for other anchors of similar condition)  to gain pull out force results on the loose bolts, where reasonably practicable.

 

[Simon Wilson]

I too am confused by the term rotational movement, then a linear dimension given to quantify this. Whilst I would agree that trying to express this to the layman in words alone may be problematic, perhaps a diagram could clear up any misunderstandings.

As a complete aside It would be interesting (but by no means a certainty of safety for other anchors of similar condition)  to gain pull out force results on the loose bolts, where reasonably practicable.

I don't think a diagram would help much either. I video would show it well. With the few that I have seen, the resin appeared to have shrunk and so the resin plug was free of the rock all around and rattling about in the hole. The 3mm I used was for a rotation of about 3mm of the diameter at the edge of the loop. Let's not get pedantic, it was only an estimate made in a cave with gloves on.

The ones that I pulled out did take some considerable force but I still maintain that it is quite irrelevant. What I think is important is to determine why they are loose. Is it because the resin is shrinking and if so, is the resin going to continue to shrink and give us a growing problem in the future?

At the moment cavers are safe if they use safe techniques.

 

[cap n chris]

I don't think a diagram would help much either. I video would show it well. With the few that I have seen, the resin appeared to have shrunk and so the resin plug was free of the rock all around and rattling about in the hole. The 3mm I used was for a rotation of about 3mm of the diameter at the edge of the loop.

https://www.youtube.com/embed/8bBEIZVZR3k

Not super-clear but taken during the course of a trip merely out of interest.

 

[Badlad]

[gmod]In response to reported posts: This is an important topic and of great interest to many cavers. The subject of anchor placements has evoked some passionate discussions in the past and will probably continue to do so, however, I'm sure we can discuss anchors and still remain civil. Please.[/gmod]

 

[Bob Mehew]

Whilst it is unclear from Cap'n Chris's video if he was playing with a loose anchor, it shows the problem we though might occur, copious movement of both the fingers and camera (substituting for his head).  I note there was no close by (to the anchor) stationary point which one could use as a reference which is what is needed when making these judgements. People may well judge movement using their fingers rather than some rigid indicating tool (like a short rod and dial micrometer) and fixed reference point. 

I accept that citing a linear distance does not appear to help when looking at rotational movement but fundamentally a loose anchor could move in any direction and in either linear or rotational mode.  Roughly speaking a one degree rotation of an anchor around its shaft would imply a rotational movement of around 1mm at the circumference of the anchor.  Suggestions for alternative words would be welcomed but please bear in mind that the average caver does not have rigid tools to take or even estimate a measurement. 

Simon's point about shrunk resin is disturbing and definitely does need further investigation.  But to spoil a joke I was going to make, the BCA puller is not really compatible with use underground, weighing in at over 40kg and best transported on a wheel barrow (see http://www.train4underground.co.uk/bolts-in-slate-testing-project/cwmorthin-test-bed/).  Simon's puller is smaller and thus better, though again not really designed for underground use.  So I fear that getting extraction forces for failed anchors is unlikely.  It is difficult to quantify what forces a resin plug may cope with but come to my lecture at Hidden Earth where I hope to shed some light.

 

[owd git]

I appear not to have a PM, sorry if this appears personal or pedantic. I simply want to reach a fuller understanding.

 

[adam]

I did Notts Pot left hand route in November and recall a very loose bolt there - part of the traverse I think. It wasn't much of a issue though - Notts is P-bolts McGee.

 

[SamT]

Simon's point about shrunk resin is disturbing and definitely does need further investigation.  But to spoil a joke I was going to make, the BCA puller is not really compatible with use underground, weighing in at over 40kg and best transported on a wheel barrow (see http://www.train4underground.co.uk/bolts-in-slate-testing-project/cwmorthin-test-bed/).  Simon's puller is smaller and thus better, though again not really designed for underground use.  So I fear that getting extraction forces for failed anchors is unlikely.  It is difficult to quantify what forces a resin plug may cope with but come to my lecture at Hidden Earth where I hope to shed some light.

DCA have some hyrda jaws (model 2000 IIRC) http://www.hydrajaws.co.uk/Products which are fine for underground use.
FWIW - the 'loose' P bolt in P8 last year and it took a hell of a lot of getting out, well in excess of the 6kN for 15 sec that a normal inspection test would require. I cant recall exactly the max rating that hydrojaws went to, before the thing started to give up, and even then, it took some serious ragging with a long crow bar to get the dammed thing out.

I'm all for the replacement of 'loose' anchors' and I whole heartedly applaud Simon for his efforts on both developing the new bolts and getting out there and replacing the bolts.

I wish we'd recorded the peak load on the above job, as it would have been good data to have and perhaps we should have videoed the whole job, just as an exercise in showing whats involved in getting one of these things out.

 

[Pete K]

There is a loose one at Garlands and in Suicide and I'd be game to help. I have a HAT-28 puller and a GoPro.

 

[mr conners]

I also applaud Sam for his use of the word "ragging".
Raunging and graunching could also be used.

 

[Simon Wilson]

There is a loose one at Garlands and in Suicide and I'd be game to help. I have a HAT-28 puller and a GoPro.

To save you Googling HAT-28

https://www.hilti.ie/medias/sys_master/documents/h99/9144283987998/HAT_28_Tester_Operating_instructions_Technical_information_ASSET_DOC_LOC_4510051.pdf

The BCA own 3 of them.

Or maybe they don't. They own some similar ones. They might own the one Sam T mentioned.

 

[bograt]

Steady on guys, the OP was asking about loose anchors placed in earlier days, info about the duration of these bolts (or resin) - - related to paper (or otherwise) records is what would be productive!.

Pull strengths and tools to do it are immaterial here and have been covered extensively on other threads.--

 

[Simon Wilson]

I did Notts Pot left hand route in November and recall a very loose bolt there - part of the traverse I think. It wasn't much of a issue though - Notts is P-bolts McGee.

Thanks Adam.
We now have reports of a loose anchor in Hardrawkin and one in Notts.

Please keep them coming. It doesn't matter if it is just a little bit loose or if you think it is safe because there is another close by. That isn't the issue. We want to know any loose anchors for research purposes.

 

[ianball11]

Diccan 

Simon, does the online CNCC form come to you via the secretary?
Perhaps there are a whole bunch of reports backing up?