Anchor testing in Rhiwbach, Bwlch y Plwm, Wrysgan and Fish Caves has now been completed (to be fair Pete finished off Rhiwbach and Bwlch y Plwm over the Summer!)
Anchors within the blue routes were visually inspected, and where appropriate pull tested with a Hydrawjaw test rig up to 6kN for 15sec. To pass the test the anchor needs to hold the load for that period without fluctuating.
All anchors that passed both the visual (i.e. recognisable, no signs of corruption, not deformed, no movement) and pull test will have a green cable tie fixed to them, any that failed (but we’ve not been able to extract) will have a red cable tie. Anchors with no cable ties may not have been tested as it wasn’t possible to fit the test rig over the anchor.
Rigging plans with all the tested anchors are available here, with the exception of Wrysgan which just needs double checking, all will be added to the Mine Inspection Reports folders available through Google Docs.
Several anchors failed during the tests (see video).
In several cases old 12mm SPIT type anchors (found in Wrysgan) pulled at relatively low loads. These all showed signs of corrosion. There are several Petzl long-life (see photo) anchors in Bwlch y Plwm that were not tested, if using these you do so at your own risk. Any expansion anchor to be tested really needs to have the anchor plate removed and the pull device attached directly to the anchoring component. This isn’t possible with the Petzl long-lifes.
Notably several anchors in Fish Caves failed, and frustratingly it was not possible to remove them. The failure mechanism looks to have been a resin/rock bond failure which suggests the holes were more cleaned throughly before placing the resin. The failed anchors are all on the second pitch in Fish Caves and so requires a slightly different approach to rigging (see rigging diagram). I’m afraid this is going to persecute the short!
Fish Caves is rigged predominantly with DMM anchors. These flex when the tested so it’s not unusual to see the resin around the head of the anchor crack (see the image of a passed anchor below). Do not be alarmed by this if using these anchors. However as will all anchors ultimately the user must make a decision if they feel it’s safe to use. Before each use check;
- Do you recognise the anchor (i.e. is it PPE, manufactured by a reputable company)
- Check for signs of corrosion
- Is the anchor set properly (i.e. nor proud of the rock)
- Check the anchor isn’t deformed or have any sharp edges (especially if tying in direct)
- Does the rock around the anchor look sound?
- Does the anchor move if twisted by hand
Please report any defective anchors through the mines inspections email account, through facebook or direct here: