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

Case for the defence

A SUDDEN, unexpected landslide caused the Heathrow Express tunnels to cave in and there was no way it could have been forseen.

So says Austrian tunnelling expert Geoconsult, which this week started its defence against Health & Safety Executive allegations that it endangered workers' lives by failing to prevent the October 1994 collapse.

Geoconsult claims a large clay slide directly above the centre of the three tunnels caused a massive 'monolithic block' of concrete and clay to fall on to the tunnels, setting off an unstoppable chain of events. This theory was put forward by defence witness Hanover University professor of underground construction Rheinhold Rokahr.

Rokahr claimed the faulty tunnel invert pointed out by the prosecution was nothing to do with the cause of the collapse and that subsequent independent studies showed that even with part of the invert removed the tunnel should have stood up for up to 80 days.

Instead, Rokahr blamed the the unexpected softening of clay between Cambourne House and the face of the down line platform tunnel. He believes the softening was caused by tunnelling work beginning on the two platform tunnels and by water soaking into the ground through a collapsed wall in an escalator box constructed under an earlier contract.

Geoconsult argues that instruments monitoring tunnel and ground movement showed readings in line with predictions until two days before the collapse. It also claims the speed of the collapse could not be predicted.

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.