Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

Knaresborough Castle secured

CONTRACTS

WORK TO stabilise cliffs below Knaresborough Castle in North Yorkshire was due to finish as GE went to press.

The castle, first documented in a 12th century text, stands on a high sandstone cliff overlooking the River Nidd.

The weakly cemented sandstone is overlain with 0.5m to 4m of unconsolidated overburden and topsoil and has been significantly undercut by the river.

Prompted by cracking of the cliff path and retaining walls, an abseil survey revealed evidence of potential stability problems. Previous cliff failures, at the base of the unconsolidated deposits, are thought to have been exacerbated by thick topsoil and ingress of rainwater.

Harrogate Borough Council, working with English Heritage, asked contractor Can Geotechnical to tender for a design and build scheme to stabilise the slope.

Following a site investigation Can suggested using more than 100 hollow, self-drilling soil nails about 5m long to ensure the overburden was tied back to the underlying sandstone.

Can won the £82,500 contract and began work in late January.

The road below the site was closed, crash decking installed above the public footpath and a catch fence built to reduce the risk to people and traffi c passing the foot of the cliff.

Can installed the soil nails with a drill rig suspended from anchors drilled at the crest line. It then used rock netting to distribute any mobilised loads within the nails, to provide reinforcement to the cliff face and to allow revegetation.

Despite having to work from inside the castle grounds while the ancient monument remained open to the public, Can was on target to complete at the end of February.

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.