Crossrail’s sprayed concrete lining (SCL) work continued this week despite the death of a worker last Friday.
The worker died at 5am on Friday 7 March while working on a sprayed concrete lining crossover tunnel in Holborn in central London.
Main contractor on that section is the Bam/Ferrovial/Kier (BFK) joint venture.
BFK referred all enquiries to Crossrail. Crossrail confirmed that the worker was spraying concrete when a piece of concrete from the tunnel fell and struck him.
Work at the Fisher Street site remained suspended as NCE went to press on Monday, but was allowed to continue at other sites.
“Assurances have been sought from all contractor sites concerning SCL works prior to construction activity commencing this week,” said a spokesman.
Tunnel boring machines are being used for the main drives on the £14.8bn scheme. But the SCL technique is being used to build 14.5km of station platform tunnels, passages and crossover caverns along the route.
With the SCL method, ground is excavated and a sprayed concrete lining applied to predetermined depths at predetermined increments.
Crossrail had said it had played it deliberately safe with its SCL design. “Given the location of the work and the profile the scheme has, this is not a project to experiment on,” Crossrail head of geotechnics Mike Black told NCE in November (NCE 14 November 2013). But Black did say that some innovation was being used in the monitoring systems.
Crossrail said a “full and thorough” investigation of the incident was underway and that the Health & Safety Executive had attended the site.
But it said it was confident that work could continue. “SCL is a well established process. SCL works are continuing,” said a spokesman.
Experts agreed that the technique was safe, but added that careful monitoring was essential. “It is a safe activity if done properly,” said Robert Ibell, chairman of tunnelling consultant London Bridge
“We have some fairly good control systems. We have done a lot of sprayed concrete lining in the UK without incident,” he said.
Ibell said he could not comment specifically on Crossrail’s use of SCL, but said the industry had to stick to some simple safety precautions generally taken by the industry.
“You do not stand under fresh concrete and you have to be very careful if you are not mechanically spraying,” he said. “You have to stand well back.”
Ibell added: “All the people involved will be trained in detecting anything untoward and making sure people know about potential problems.”