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

St Johns Wood

The first shaft was completed last month on the longest tunnel built in the UK since the London Ring Main a decade ago. The 10m diameter shaft at St Johns Wood in north London is the first of seven such structures on the National Grid's London Connection project. The 20km tunnel will link St Johns Wood to Elstree and carry 400kV electricity power lines. Contracts for the main tunnelling works will be awarded by October, from a shortlist of Amey, Amec, Miller and Murphy. Construction of the 3m diameter tunnel will start in February 2001 using earth pressure balance machines. The precast segment lined tunnel, designed by Brown and Root, will pass through mainly London Clay at a depth of 20m, with the 6km northern section in the Lambeth Group. 'It was important to keep the tunnel out of the chalk, ' said Brown and Root project manager Michael Francis. 'We don't anticipate problems in this section but will use bolted segments and grouting.'

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.