Removing Sleeve Anchors (SPITS etc…)

I guess this post is a bit of a continuation from the blog post I did about pull testing SPIT type anchors in 2015. Sorry it has taken me so long to get round to doing this!
The original post can be seen here: http://www.peakinstruction.com/blog/pulling-spit-anchors-back-garden-test/.

One of the points of that testing was to ascertain if the sleeve anchors could be removed from the rock in a cave or mine to either de-clutter the wall or allow a resin anchor to be placed in the same location. This is important from a conservation point of view, these sleeve anchors are a bolt rash on the walls of our caves and once stripped of threads, are there forever…. or so I thought.

Jump ahead to now. Simon Wilson has developed the IC Resin Anchor in the Dales and his website has expanded to become a good resource of information relating to the installation and removal of anchors. Most relevant here is the method that he uses to remove old sleeve anchors, one which I am shamelessly copying here in an effort to spread the knowledge and encourage the tidying up of pitch heads. Simon’s site is here: http://www.resinanchor.co.uk/5.html.

I started with the original block of Stoney Dale limestone used for the original testing in 2015.


 

 

 

 

 

Method used:

  1. If required, dress the rock near your anchor sleeve with a chisel to create a flat area for drilling.
  2. Drill a 6 or 7mm hole immediately next to the anchor sleeve.
  3. Drill a second hole parallel to and as close to the first as possible.
  4. Bore out into a slot using an old drill bit and some wiggling.
  5. Tap the anchor sleeve into the slot using a cold chisel or old screwdriver.
  6. Remove the anchor from the hole. This may well need some jiggling about or a bit of extra chiselling. If possible, screw a bolt into the sleeve to aid extraction.
  7. Fill hole with resin or drill out for the installation of a new resin anchor.

Shown with a SPIT 12mm self drilling anchor:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SPIT 12mm self drilling anchor that had sheared off in a previous test:


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Another SPIT 12mm self drilling anchor that had sheared off in a previous test:


 

 

 

 

 

 

 

 

 

 

 

This removal method works well once you’ve had a little practice and was far less destructive or time consuming than pulling the anchors out with the HAT-28. I also used the same method successfully to remove 10mm lipped sleeve anchors as well (HKD / drop-ins etc…) although have no photos.
As I was drilling so close to the sleeves, occasionally hitting them, this was very hard on drill bits. I melted the head off my cheap 7mm half way through and swapped to the 6mm bit. I’ve just ordered some quad tipped bits from Hilti in the hope that they are tougher. I’ve only ever destroyed one of them in the tough welsh rhyolite of Parc mine.

The remaining triangular hole can then be cleaned out and filled in using an expired resin cartridge with some limestone dust thrown on. It won’t disappear 100% but will be a huge improvement over the old rusty sleeve.
If you plan on re-using the hole for a new anchor, try to position your slot to the intended orientation of the head of a ‘P’ style resin anchor. Once the anchor is placed, make sure the whole hole is filled with resin leaving no voids. You can’t use the SPIT resin vials for this job as they have a set quantity of contents, you will need to have a resin cartridge gun to fill the irregular hole properly.

I hope to begin removing some of the decades of old sleeve anchors in sites now resin bolted and potentially earn some karma points back for anchors of this type that I myself have placed in the past prior to my ‘enlightenment’.

Thanks for reading.

Pulling SPIT anchors – Back garden test

This week I thought I’d embark on a little back garden test of some brand new SPIT self driving anchors and some SPIT Grip 10mm sleeve anchors. Both take a normal M8 bolt and hanger and can be found in caves and mines across the UK. The Grip sleeves are placed with a drill and only require a 10mm hole, the caving SPIT sleeves can be placed with a hand driver or drill/driver combination in a 12mm hole. Recently there have been discussions about potentially removing superfluous spits in some committees. The idea being that any old ones could now be removed where resin bolts are installed nearby.

I made a quick trip to the Hitch N Hike emporium of shiny things and located a lump of suitably good limestone to transport to the back garden. I set a number of each SPIT anchors into the limestone using the standard installation method for each. For testing I used my freshly calibrated Hilti HAT-28 unit attached directly into the sleeves via a hardened M8 bolt.

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Bolt 1, 12mm:
This didn’t make it as far as the testing. Unknown weaknesses in the boulder cracked open as I was hammering the bolt home and the placement failed. Annoying but it does serve to highlight the issues of using any expansion anchor, especially shallow ones like these. Another tick in the ‘for’ column for resin bolts.

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Bolt 2, 12mm:
A normal placement in a better part of the rock. I tested this by adding force in 4kN increments until 15kN was reached and the bolt started to slowly extract from the hole. Every time the force increased beyond 15kN the bolt pulled a little further out until it ultimately was removed intact from the rock at a little over 15kN.

Bolt 3, 12mm:
A normal placement as with Bolt 2 in good rock. Force was applied in the same way as before up until about 18kN when a small cracking noise was heard. I very gently increased the load expecting the cracking might be the limestone surface under the metal legs of the puller. At 19kN the bolt let out a loud crack and the tester jumped free of the block. “Great” I thought, it pulled out. Nope. The SPIT sleeve sheared about 15mm from the top, the remainder remaining set in the limestone block.

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This was a first for me and I came to a couple of possible conclusions.
1: The sleeve was defective and the break was a freak occurrence.
2: The bolt I used was not screwed far enough into the sleeve and as such mainly applied force to the top section of the sleeve.

Bolt 4, 10mm:
This anchor came out very quickly. The bolt was extracted intact at 5kN. On later inspection the internal cone had not been driven to the full depth, perhaps 6mm short of the end of the sleeve. I suspect this made for a poor expansion in the hole and hence low removal force was required.

Bolt 5, 12mm:
As for Bolt 3, this sheared in the hole, leaving over half its length still in the placement. It sheared at 20kN. I suspect that a longer bolt would give a different result for this type of test. The bolt used was tightened to the same depth as a standard hanger plate attachment would have been when in normal use. The next test would use a longer bolt.

Bolt 6, 12mm:
A longer bolt was used to test this placement. The bolt was screwed in until fully inside the sleeve but not tightened as I did not want to begin to force the cone out the back.
This test did not result in bolt failure. The sleeve was extracted 1mm from the rock as the force reached 18kN and at 20kN was still holding strong at that position. This is the maximum force the HAT-28 can apply.

Bolt 7, 10mm:
This sleeve had it’s cone driven harder when setting, to the point that the sleeve began to push into the drill hole slightly. The tester removed this bolt from the rock at 9kN and it came out intact. The cone was found to be 4mm from the end of the sleeve.

Bolt 8, 10mm:
This bolt was set very hard indeed. The cone was pushed completely into the back of the sleeve with some serious hammering force. The cone was 3mm from the back of the sleeve. This bolt was extracted at 13.5kN and came out intact. The rock around the placement failed as the bolt was nearing full extraction.

Summary:

Bolt 1 12mm no result
Bolt 2 12mm extracted at 15kN
Bolt 3 12mm sheared at 19kN
Bolt 4 10mm extracted at 5kN
Bolt 5 12mm sheared at 20kN
Bolt 6 12mm no failure at 20kN, 1mm of extraction
Bolt 7 10mm extracted at 9kN
Bolt 8 10mm extracted at 13.5kN

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Conclusion
Nothing can really be drawn from that info as it is such a small sample. The main learning points I have taken from this are:

  • 12mm sleeves may shear when a bolt is not inserted fully.
  • 10mm sleeves extract at lower forces than 12mm sleeves.
  • 10mm sleeves must be driven home very well to make their higher strengths. This is not always possible as the sleeve can be pushed into the drill hole if not drilled to exact depth*.
  • All shallow expansion anchors can cause the rock to crack near the surface and no placement at this depth can be 100% guaranteed until the cone is set.
  • There are big variations in the extraction forces which depend on many variables during the installation..
  • No sleeve anchor can be removed with 100% certainty meaning that they will likely remain in the walls of the cave or mine forever.

*One of the selling points for this type of anchor sleeve is that they have a lip to prevent them slipping into over drilled holes.

I’ll be doing some further testing soon and will be taking the rig to some corroded anchors already in situ for a more real world test.
Finally, please consider not using SPIT sleeves or any other brand in places that get high traffic or will likely be resin bolted in the future. They will litter the cave wall forever (as can be seen in places like Garlands Pot and P8). A resin bolt can be removed and the hole reused. A 12mm through-bolt can be over drilled and hit into the hole and covered with resin. SPIT sleeves are likely visible forever.

Pull Testing Ground Anchor Pins

It is quite common that where you need to anchor ropes to things, there are no natural things there to anchor to (like boulders). Climbers and cavers get round this by installing bolts and/or ground anchors. A ground anchor is a (hopefully) long length of angle, pole or bar that is driven in deep and (hopefully) can hold a load due to it’s friction with the ground. These are most commonly seen at the top of moorland cliff faces, installed by rock climbers as a top anchor to abseil from or belay a second. As part of the process of looking into developing a mobile zip wire / team building exercise we had decided that some form of ground anchor would be needed. There are a number of options, from home made to high cost but we opted for the tried and tested ‘mooring pin’ approach as used by mountain and cave rescue teams.

Now, just before people get a bit worried, this is not for life preserving! These pins are intended to act as guy lines for a tripod structure in poor, rocky soil.

Myself and Beth hammered the 50cm long 16mm galvanised steel pins in, one to 1/2 way and one to 3/4. Both of these pins came loose with very little force, about twice average body weight. We then drove the pins in up to their necks and set up a 10:1 pulley system from the back of my van, Brick.
The pins held well but at about 300kg they bent and pulled out. Even rigging a pair in a V made little difference, in fact I was dismayed to see my £20 pins bent after about 5 minutes of testing.

The final test involved setting the pins up as done by MR and CRO teams. We needed a 3rd pin so I used a section of what looked like 14mm rebar fencing spike. The 3 pins were hammered in full length in a direct line to the load. A rope was then used to tie each in line, stacking the pins with clove hitches seemed easiest. The force was applied to the front pin which, as it moved forward to take the strain, came tight on the 2nd pin which in turn came tight on the 3rd. The 3 pins worked as one and we were able to pull a force of 4.84kN with no failure of the anchor.
We stopped at that as we were now in danger of breaking the smaller pulleys used in the MA system and my van was beginning to move.

In conclusion:
Good news – the 3 pin method is very strong and would make a suitable ground anchor for guy lines but also, if backed up to a second system, would be okay for rigging safety lines from. Also, fencing spikes are seriously strong!
Bad news – £20 worth of 12 hour old pins are now bent like beech twigs. These just were not up to the job, poor steel. I’ll be picking up some fencing spikes and using them in the future.

Testing Ground Anchors

Testing Ground Anchors

New Bolts at Pindale Farm

Recently I have been spending a lot of time swinging about on the surface, either through testing knots or coaching SRT skills. For all of this I’ve been using the excellent tower facility up at Pindale Farm near Castleton.
The SRT platform offers scaffolding bar belays and back-ups and the surrounding walls of the old mining buildings are equipped with many 8mm anchor sleeves (Spits) and a few alloy Troll hangers. You can rig just about any permutation of SRT pitch your brain could possibly come up with.
Using the tower over the past few years I’d noticed the deterioration in some of the anchors and as I was such a frequent user I thought some of the replacement anchors should be paid for out of my pocket.

Yesterday (19th March 2013) I managed to procure both equipment and assistance.
Jez Parr CIC (contact) was kind enough to loan me his SDS drill and all the bits for the job.
Nigel Ball CIC (Website) donated half of the anchors and 90% of the expertise in the operation.

We placed 4 new Petzl P38 Longlife anchors on the main wall of the facility; a line of 3 forming a traverse and pitch head which then drops to a rebelay or deviation on the 4th anchor.
We also lubricated and cleaned out all of the 8mm sleeves with a threaded tap to give them a new lease of life.

The tower is now a mix of anchors and can be used with or without hanger plates. Please bare in mind that the tower is equipped by volunteers/individuals and is on private land so booking is essential. Users are reminded to check the anchors they use are safe before commiting their life to them as they would underground and that anchors should never be used alone but as part of a safety chain.
All bolts will fail at some point.

Pindale Farm is an excellent place to stay in the Peak for caving or any other reason. They have camping and bunkhouses on their site as well as the excellent SRT tower.
http://www.pindalefarm.co.uk/

New bolts circled:Pindale Tower