Merged topic - Spit and BP bolt removal/replacement

[Antwan]

Politics aside, When re-equipping a route with resin anchors is drilling out the old spits and re-using the holes a good or bad idea?

The route I question is traverse that is little used next to a CNCC eco anchor rigged pitch.

[Badlad]

I would suggest that;

From a conservation point of view this would be a very good idea.

From a practical point of view it is more effort to remove the old spits.

From a safety point of view I expect there are some issues with stressed rock, but I suspect that the deeper and wider hole size of the resin anchor should mitigate any of these problems, especially if the resin anchor only stresses the bottom of the hole.

Then again I'm no expert 

[SamT]

Pretty much what he said.

Its a bit of a faff trying to remove old spits and they are not too unsightly once they are old. 

I think the zone of stress from them is cone shaped..from the bottom of the spit back towards the surface of the rock if that makes sense. 

[SamT]

[SamT]

Hence if you think about how shallow a spit is.. it gives you a rough guide to how little of the stressed area your resin anchor will pass through.

[andrew]

I believe the stress cone disappears when you remove the old anchor, however there may still be damage. Given that, as has been said they are very shallow so it is limited.
Yes it is a real pain to remove an old spit or equivalent, and does take longer, but really on the scale of time for use and coservation of the cave, should we not be trying to replace as much as possible.

Slightly more concerning is if people are not reusing resin anchor holes, which I ave heard rumours (but no evidence)

Also the BP anchor that is part of the current BCA scheme have a spiral that completly fills the hole, so the resin cannot be drilled out. Before I place anymore I would like to  know how these are removed and the hole reused? (Don't answer in this thread, I will start another)

[andrew]

The BP anchor that is part of the current BCA scheme have a spiral that completly fills the hole, so the resin cannot be drilled out. Before I place anymore I would like to  know how these are removed and the hole reused?

[Antwan]

Thanks, pretty much what I remember from talking to Chris whatshisface from DMM about the ECO part of the eco anchor partly been about re-using holes ( about 7 years ago now maybe?)

Just wanted to make sure and canvas a few opinions

[Bob Mehew]

Andrew beat me to it.

Sorry to say I think it is a little more complicated than Sam's diagrams imply.  There are two states, one when the anchor is not loaded and the other when it is heavily loaded.  Sam's diagrams reflect a theoretical heavy loading condition which I never managed to bottom out.  I believe the 90 degree cone angle is based on a simple argument reflecting the inverse of a soil spoil heap (where the soil has no cohesive strength).  But I have also come across a 60 degree cone angle and not been able to get a handle on why that angle.  (I suspect it reflects the degree of cohesion of the rock or compressive strength.) That is why you get slightly differing arguments that you should not place anchors closer than either 1.5 or 2.0 times the depth of the anchor so as to avoid overlapping the cones.

But the anchor spends most of its time unloaded and thus for a spit (or expansion anchor) the stress on the rock is localised around the bottom of the hole. I don't have comparative strength data of rock and metal to say whether the rock is so stressed as to cause it to suffer deformation of some form or it is just the metal which deforms.  Looking at some expansion anchors, my guess is the metal suffers, not the rock. 

A point first made by Simon Wilson is that post resin failure, the Bolt Product anchor appears to transfer its load much further up the shaft (at the point where the shaft switches from straight to coil) whilst the DMM Eco anchor does near the base (where the tangs are located).  I await Simon's report on reusing holes with his anchors.  I have no recollection of tests being done on old spit holes.

There is also the point that often the best spot for locating the anchor is taken by the spit, so devising a simple means of extracting it would be beneficial not just from a conservation view point. 

[Pete K]

On the subject of removal of old Spits - it my be worth speaking to Bob Dearman (DCA Equipment Officer). He recently proposed removing old Spits that were no longer required so I assume he has a method for doing so.

[Bob Mehew]

I am not aware of any work having being done to extract them other than by using an anchor puller.  (I welcome being proved wrong.)  But as a starting point, one has the same problem with all resin anchors with a need to drill through both metal and resin.  In theory one should be able to design a simple anchor puller which could be used in confined spaces.  Simon Wilson's puller is much smaller than the BCA one and has at its heart the mechanism from a screw jack.  But that used a meter long handle to apply the force.  (I recall attempts using a clutch puller were blighted by the lack of a long enough handle.)     

Whilst I can't speak on behalf of BCA's E&T Committee, I for one would look favorably on an application to fund the building of such a puller.

[andrew]

Hmmm, that is what I thought.
DMM anchors: I have removed a few, and you can get a 5mm bit (smallest sds I could find) and drill down the sides, taking out the resin, only just clipping the metal. A bar can then be used to twist the anchor, breaking the rest of the resin. Then the bca test puller can pull them out, although it still requires it to be wound up to max (10KN from memory) then it takes minutes for it to be fully extracted.
With the BP anchor, a metal drill could be used, but the worry would be that it would break up, when the puller is used. I have some resin that is a couple of months out of date, maybe I will try it on an anchor.

[Bob Mehew]

One problem with BP anchors is you will have to initially drill through resin before you get to the metal coil.  And to avoid confusion, the 10kN puller you refer to is manufactured by Hydrajaws see http://www.hydrajaws.co.uk/ where as I was referring to the BCA manufactured puller, see http://www.cncc.org.uk/documents/anchor_test_316_date_23_november_2013.pdf which is a totally different beast.  (I took it underground in a wheel barrow.)

I concede we need to do some tests with BP anchors in 18mm and possibly 20mm holes to allow for damage to the rock hole side whilst extracting the anchor.  I also concede one probably does need to do some drilling to weaken the BP anchor to avoid breaking the rock surface which is experienced when just pulling them.  (It is worth noting Simon Wilson has experienced little if no rock damage in extracting anchors as part of his test program.)

[Mark Wright]

You can put a 20kN gauge on a Hydrajaws pull test rig which should make extraction a bit easier.

Mark

[Badlad]

Yes it is a real pain to remove an old spit or equivalent, and does take longer, but really on the scale of time for use and conservation of the cave, should we not be trying to replace as much as possible.

Slightly more concerning is if people are not reusing resin anchor holes, which I ave heard rumours (but no evidence)

I was told that 20 -30 Peco anchors which were decommissioned in Rowten Pot Gully have been hammered flat and smeared with resin and mud as the favoured option.  I believe that the route has now been rebolted with the new BP bolt as well, although I have not seen this myself.

More here http://www.cncc.org.uk/documents/PECOAnchorDecommissioning.pdf

[Simon Wilson]

We have two threads on almost the same topic so I'll stick to this one.

If a Spit has a good thread in it then it is quite easy to pull it out. If the thread is gone then I don't know how to do it and would welcome suggestions. I've been shopping around for a diamond core drill that will drill around a Spit. It might be worth a shot. You would only need to drill about 25mm deep then you could probably get the rest out with a small chisel.

In the early days of the DMM Eco hanger one of the selling points was that at any time in the future they could be removed and the hole reused and that has proved to be true - the clue is in the name. Nobody has come up with a method of a removing a BP anchor.

On my website I say that I intended to test IC anchors installed in previously used 12mm holes. Yesterday we pulled out four such anchors. I haven't had time to write up the results on the website. But I can tell you the anchors pulled out at peak loads better than the first time the holes were used. I expected that result and I will explain why on the website. The lowest of the four pulled out at 34.91kN.

We also pulled out an IC anchor that had been installed in an 18mm hole. This pulled out at 35.14kN. I intend to test a few more in 18mm holes.

I am in the process of making a compact puller that can be used in caves to extract anchors. I want to be able to demonstrate that IC anchors can be extracted without damage to the rock because I think that is an essential requirement of any resin anchor for caving or climbing.

[cavermark]

I was told that 20 -30 Peco anchors which were decommissioned in Rowten Pot Gully have been hammered flat and smeared with resin and mud as the favoured option.  I believe that the route has now been rebolted with the new BP bolt as well, although I have not seen this myself.

More here http://www.cncc.org.uk/documents/PECOAnchorDecommissioning.pdf

What about drilling through the anchor head with a cobalt drill bit? 

Is a portable grinder (with a suitable mask and rope access techniques) really not an option? Makita do a grinder that fits the same LiIon batteries as their SDS drills now.

The resin splodging seems pretty unsightly, especially for waterwashed sections (and would make future attempts with portable grinders or pulling devices pretty much impossible)....

[Simon Wilson]

It would be impossible to drill the anchor enough the get it out.

Pulling out a BP anchor will never be an option because the design of the BP anchor means that the rock breaks when it's pulled out.

[andrew]

As others have said, one if the big selling points was that the anchors could be removed, mainly so we did not run out of rock to place in. Yes it takes about an hour, but if we are to conserve this delicate environment, it should be done. (And I have done it myself so I am putting my money where my mouth is)

As for spits although not available a couple of years ago, things like this are available

http://www.amazon.co.uk/Marble-Ceramic-16mm-Diameter-Drill/dp/B0053OFGNE/ref=sr_1_6?ie=UTF8&qid=1416249091&sr=8-6&keywords=16mm+core+bit

Hopefully will work, anyone think of any reason why not, I think I will get one.

Spits: if the thread is good and they were a hand spit (12mm) yes a puller with a punch down the centre works. Drill spits are coned the other way, and the thread breaks. Cobalt drills dud very little.

[Bob Mehew]

Typically we are talking about 30+kN to extract Eco & BP anchors.  You need to weaken the placement before pulling.   

[Simon Wilson]

Andrew,
Yes, that's the sort of core drill but I think you will need to get one with a 12mm bore. You will need a water bottle to wet it. Please have ago and let us know how you go on.

I'm hoping my puller will pull out a DMM in a few minutes.

[Bob Mehew]

I speak without practical experience but my memory is grinding heads off was considered to be dangerous given you almost certainly were hanging from a single rope which is likely to be located in the work area.  Would I be right in suggesting industrial rope access techniques require a number of anchors so as to organise several ropes to the work location in order to get them out of the way of the grinder?  One could use a hacksaw but that would take a fair amount of effort (and probably spare blades).

Extracting the Eco or BP anchor either requires one weakens the resin by drilling into it so as to enable the anchor to be pulled out with a much lower force or else one removes the head and drill in to remove the whole lot.  BP anchors are know to crack the surrounding surface rock on extraction without prior weakening.  I don't think anyone has tried weakening the resin before pulling them.  Eco usually came out cleanly with (or without) prior weakening the resin.

The only challenge I foresee with a core drill is build up of swarf / rock & resin dust. 

[nickwilliams]

A battery angle grinder was tried for removal of some of the Peco anchors, IIRC, but the resin quickly gets heated by the metal work and the resulting fumes in the confined space of a cave were found to be intolerable. Mind you, I don't know if this was using ultra thin discs.

Achieving the kind of pull forces required to simply extract an anchor with anything less beefy than the puller used for the test programme will not be easy. The forces involved are significant: for example I tried a straight pull with a 10t hollow hydraulic cylinder and this bent the eye on the puller and easily sheared the M12 8.8 bar I was using as the pull rod (the biggest that would fit through the hollow cylinder). Obviously stronger materials are available but this rapidly becomes a custom made solution requiring considerable effort and expense.

[Simon Wilson]

If cutting the heads off resin anchors or bending them over became acceptable we would end up with bolt rash. We should not install any anchor which can't sustainably be removed.

In the case of Spits, diamond core drills will only drill rock. The dust is removed with water.

[Simon Wilson]

Achieving the kind of pull forces required to simply extract an anchor with anything less beefy than the puller used for the test programme will not be easy.

I'll let you know how I go on.