25 April 2016

The challenges of operating under central London – and an innovative way of propping sprayed concrete tunnels – formed Costain’s contribution to this year’s British Tunnelling Society Young Members conference.

Senior Engineer on the Bakerloo Line Link (BLL) Andrew Irwin, together with Apprentice Civil Engineer Luc Williams, presented at the annual event.

“I thought it would be a great opportunity for Luc and I to showcase the fantastic work we are completing on the project and the challenges involved in constructing the BLL,” said Andrew.

The BLL, which will provide interchange and step-free access between the Crossrail station box and London Underground’s Bakerloo Line at Paddington, has to thread its way through a network of existing below-ground infrastructure. The BLL passes under the 150-year old Brunel train shed at Paddington, as well as under the Bakerloo Line.

“Luc has been on the project from the very start. He presented on the sprayed concrete element and demonstrated how we are overcoming the challenges of constructing our new tunnels and structures around the vast existing infrastructure in the Paddington area.”

For the first time, the conference had a separate poster presentation where young engineers could define and explain interesting problems they had faced in their careers.

Costain’s entry in the presentation, produced by Andrew, was based on his previous project. This focused on the challenge of connecting sprayed concrete-lined adits on the Crossrail C360 contract, with the main Crossrail running tunnels being constructed by another contractor using a tunnel boring machine (TBM).

Creating this type of junction normally requires access to the main bored tunnels so that the junction can be supported with propping, but on this occasion, such access was not available as work was still continuing within the main bored tunnels. So, a new method had to be found.

“Our solution was to utilise pocket excavation: ground support provided by a sprayed concrete lining and installing props within those pockets,” said Andrew. “All our propping was completed from within the sprayed concrete lined tunnels, so no interface at all was required with the TBM-bored tunnel works. Our solution was safer to install; more efficient in terms of cost and programme; and removed potential interface clashes with a third-party contractor.

“The conference was attended by young engineers working within tunnelling, with representation from contractors, designers and researchers. We received positive feedback from the audience and the variety of disciplines generated further interesting discussions and opportunities for networking throughout the event.

“Luc and I enjoyed sharing the innovative solutions we are using to overcome the technical challenges of constructing the Bakerloo Line Link.”

Caption: Andrew Irwin (left) and Luc Williams received good feedback from the audience at the British Tunnelling Society Young Members conference.

Ends

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