UKC

So caving is currently going through its second major burst of rebolting with glue-in anchors. In the 90s a large number of DMM Eco anchors were placed (estimate of 2500 or so?). BCA regions are now placing BP 8mm 100mm bolts and placing these. Bolts, training and expenses are paid for through the BCA anchor scheme, which also tests and 'approves' bolts. Obviously caving presents a few extra difficulties when bolting - for example, getting everything dry is probably impossible in some cases, so resins which cure when wet are used.

Quite a few of the 90s vintage DMM anchors are now wobbly, and have broken the connection between rock and glue. I have read that this is more common for the old ECO anchors (possibly due to not cleaning the holes properly or resin shrinkage). There are enough that they get reasonably regularly reported and queued for replacement.

My suspicion is that in climbing there are vastly more glue-ins, possibly vastly more Eco anchors still knocking about, and far fewer loose/wobbly glue-ins (at least fractionally)? Or maybe the good climbers of the world are just a bit quicker at replacing them...

A caver has also designed a glue-in anchor called an IC anchor designed to come cleanly out of holes when pulled, allowing reuse of the holes. This is for conservation, and so has become the favoured choice in Yorkshire, although there may be supply issues.

Any thoughts?

In reply to andrewmc:

Although I have no experience bolting anything, having read the info about the IC anchors here; http://www.resinanchor.co.uk/index.html
They look like really well thought out bolts and being able to use smaller holes seems beneficial.

In reply to gethin_allen:

Ah well! I´ ve corresponded with the designer of the IC bolt as well as with the caving associations since I supply them. The concept is (relatively) sound but a bit wierd at the same time. Probably the most expensive way possible to make a bolt as well!

The objective was to remove the bolt without the rock cratering on the surface so the IC bolt removes the mechanical bonding to the resin in the upper part of it´ s length and thus deliberately promotes failure between the bolt and the resin, whether making the bolt/resin bond weaker is a good idea is a matter of opinion!

The logic behind this is a bit peculiar however, being able to pull the bolt requires that it has a strength of at least 35kN, that is, it may not be damaged or corroded in any way which leads to the obvious question of why remove it?
Alternatively if the resin has failed then any bolt can be removed without damaging the rock.

As long as the bolt is physically stronger than the resin bond, either to the bolt or to the rock they can be removed without the characteristic cratering on the surface, simply by changing the design of the puller baseplate to a small hole rather than the more normal tripod system required for strength testing. We have removed mechanical anchors incorrectly installed in a sandstone structure this way without any surface damage.

Having a small hole for installation is sometimes good, sometimes bad. To get sufficient strength from the rock/resin interface you require a minimum surface area and the only two options are a larger, shallower hole or a smaller, deeper one. Given strong enough rock and the right resin system you can go suprisingly small, down to under 4cm but in usual limestone you need around 8cm. We make an 8mm shaft bolt which can be installed in a 9mm hole BUT you really need to be sure of your gluing system in the shorter (8cm) lengths.

Our (Bolt Products) bolts are the only ones that passed the BCA tests which are more stringent than for EN959. All failed at the resin/ rock interface at around 50% of the actual bolt strength.
The IC bolts are not manufactured for sale to climbers, they are not certified to EN959.

In reply to jimtitt:

They look like they present a very good option should bolts ever be placed at stanage or the likes.

In reply to andrewmc:

Surely the ultimate solution is to use a portable grinder to grind a perfect nut placement which can be used for ever and ever? Are there the same concerns of unslightliness of fixed gear in caving as there are in climbing?

In reply to Toerag:

I suspect your articifial nut placements would have a distressingly short life expectancy compared to a bolt if fallen on regularly. Smaller area of rock being hammered/ground against by a bit of metal that isn't resined into place so moves every time. Might get away with it on good granite; wouldnt fancy it much on lime or most sandstone.