[shark]

https://www.thebmc.co.uk/warning-issued-over-slate-bolts

Climbers are warned about potential bolt failures in the slate quarries of North Wales. The BMC advise climbers to use great caution with any expansion bolts used for protection and in particular for lower offs on popular routes. Resin bolts are not affected.

After a 10mm expansion bolt was reported to have failed on a popular route lower off on the Sidings, locally based instructor and coach Mark Reeves started checking bolts and lower offs on the most popular routes in the quarries. Mark used a hydraulic bolt testing rig to pull test a number of bolts. Several things became apparent:

A number of 10mm expansion bolts pulled out at very low loads.
Popular route lower offs are badly affected.
Any bolt which can be moved must be considered dangerous.
Wet weather may accelerate the wear caused by heavy use leading to bolt failure.
The local bolt fund (NWBF) has been supporting volunteers undertaking this testing and urgent remedial action replacing loose bolts on the most heavily used routes with resin bolts.

This work is being done by volunteers with limited resources, so it may be some considerable time before all potentially dangerous bolts are checked and replaced.

TREAT EXPANSION BOLTS ON SLATE WITH EXTREME CAUTION

You may be asking how has this happened? During original testing the results with both 10mm and 12mm expansion bolts were good on slate. Follow up tests made more recently confirmed that when initially placed, expansion bolts appear to meet UIAA standards.

With heavy use, the softness of slate appears to allow degradation of the rock leading to movement and weakening of the bolt because it no longer securely fits into the drilled hole. In addition, after wet conditions it appears that water can infiltrate the slate,  softening the rock and speeding up the wear process caused by heavy use.

Resin bolts do not stress the rock except when loaded and spread the load more evenly so in future will be the only bolts recommended by the BMC for use on slate.

Big thanks are due to Mark Reeves for a huge amount of testing and bolt replacement. Check out his website

Contact the NWBF and donate by clicking here.

[danm]

This article has been updated - the facts are the same but the warning slightly toned down a little. In summary, a few loose 10mm lower off bolts have pulled out when tested at very low loads, so be careful.