We have been granted kind permission to explore mines on a farmers land. First adit ,we hit a natural pot with a sizable chamber visable at the bottom .what are people toughts on the approach to bolting this initially? we have disscussed the many options from concrete screws to chemical anchors,but some of us dont feel happy with the concrete screw option.given there is a high chance caver access would be granted in the future, i was interested in peoples opinion of weather to pop in some temporary anchors or bolt it properly from the start?all opinions welcome,including anchor selection/resin.
Bolting
- Thread starter markpot
- Start date
JohnMCooper
Active member
I've always been wary of using pilot holes with a hammer drill as it puts all the stress on the edge of the tungstem carbide tip. No idea whether it really matters but would welcome feedback.
I'd personally start off with concrete screws for the original exploration (I used 8mm Fischer FBS II recently and they were really good), then swap them for glueins if I wanted it to be more permanent. I did exactly this for a project in Swaledale and it worked really well - I redrilled the 8mm hole with a 16mm hole and used the larger Raumer glueins from Tony.
I've got a load of spare concrete screws if you want some?
B
I've got a load of spare concrete screws if you want some?
B
MarkS
Moderator
+1 for concrete screws. Not a long-term option, but by far the best conservation-wise before deciding whether more permanent anchors are warranted.
If any of your group are unhappy with concrete screws, have a read of this and this, and consider on what basis you might be happier with throughbolts or expansion anchors.
If any of your group are unhappy with concrete screws, have a read of this and this, and consider on what basis you might be happier with throughbolts or expansion anchors.
sinker
New member
MarkS said:
For reasons that I don't have time to go into here and now, under NO CIRCUMSTANCES should you use concrete bolts / thunderbolts / anchorbolts, call them what you will.
When I get home later I'll expand on the reasons but PLEASE put that thought out of your head right now.
You need STAINLESS throughbolts or STAINLESS resin P-anchors.
As for "temporary bolting"; no. do it once and do it properly.
I've only used concrete screws a couple of times in caving - lots in construction work. I have read the testing done by Simon Wilson and discussed their use with other knowledgeable cavers. I was convinced that these are a really good short term option for rigging especially with the conservation arguments and reuse of holes. In the fullness of time and when a route is settled on then sure there are better fixings such as resin bonded anchors etc. I'll be interested to read the reasons for your dislike of them and how that conflicts with other opinions and testing.
pwhole
Well-known member
If access is almost certain, and the placements are known to be perfect for all the right reasons, go ahead and do the permanent stainless options. As for the temporary options, I've been using Excalibur bolts for ages with no issues, including a test batch left loosely in the wall of a very wet shaft for over a year that showed zero corrosion on removal, but I'll wait for sinker to get home first 
Pete K
Well-known member
markpot said:
I've used good quality Fischer concrete screws in limestone and slate for exploration and bolt climbing and if done well, with suitable backups, they are an excellent anchor when you think you may need to put a permanent solution in place in future but want to check it goes first. Stay a million miles away from Spits, they are a relic of the past.
If you do choose to go down the route of resin anchors, feel free to contact the DCA. I'm happy to chat you through the commonly used trusted combos and DCA could potentially offer some assistance.
Pete K
Well-known member
I don't believe they tested concrete screws. This was a body of testing done to approve the BCA BP resin anchor in slate, as previously it was only tested and installed in limestone. IIRC Gethin tested BP, IC and expansion anchors in 3 different slate bodies.
Some details can be seen on his site: https://www.train4underground.co.uk/.
Some details can be seen on his site: https://www.train4underground.co.uk/.
sinker
New member
pwhole said:but I'll wait for sinker to get home first
I still don't have time to fully expand. I'll let the thread run it's course, but again, PLEASE don't use concrete bolts.
They'll be fine for a couple of years then they'll get forgotten about. Next thing some future explorer will come along and rig off them and fall to his death.
With ANY LUCK he would put a spanner on it first and check the tightness. Then when he nipped it up the head would shear off (which is what happens with them) before it was rigged.
The torsional stress in those bolts is unbelievable. If the hole is a few microns too tight, due to a bit of residual dust or slightly worn drill bit, then the torque applied can put so much torsional stress into the bolt that the end of the thread is 1/4 of a revolution behind the head. This is why the heads snap off them. Torsional stress and stretch. look carefully at the shank under the head and the casting where the thread stops and the shank starts. the ALWAYS shear off in either of those two locations.
Final point, although I could go on all day, I have yet to see any of this type of bolt (Hilti / Fischer / Ankabolt etc etc) where the manufacturer actually states that they are suitable for suspending a human being on.
That final point is all you need to know.
As a Temporary Works Designer / Co-ordinator I can sort out all sorts of temporary works designs which use this type of bolt for holding down shutters, hand rails (in a load-share situation), soffits etc but in the last 20 years since their widescale introduction I have yet to see a design which approves them for use in suspending a human being in an access, fall restraint or fall arrest situation.
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