17 November 2015

The Costain-Vinci Construction Grands Projets Joint Venture team has reached a key milestone in its £85 million construction of the Shieldhall Tunnel in Glasgow for Scottish Water.

Geotechnical specialist Bachy Soletanche has completed the mammoth task of installing the project’s 675 piles in just three-and-a-half months. The piles play a vital part in the preparation of the ground for the next stage of the project: the start of the tunnel drive.

The work carried out by Bachy Soletanche included the construction of cased secant piles (CSP) for the first shaft of the tunnel, the service chamber and tunnel boring machine launch chamber, along with 400m of continuous flight auger (CFA) contiguous piled walls for the cut-and-cover section of the tunnel. The reinforcement cages placed in the piles each weighed approximately a tonne each, were more than 15m long and were filled with nine cubic metres of concrete.

As well as being technically challenging, the work had to be carried out within a residential area and in a restricted workspace. The two 25m-tall piling rigs – the 100 tonne CSP and 70 tonne CFA - two huge service crawler cranes and concrete pumps had to work in an area equivalent to the size of just three full sized football pitches.

Brian Walker, Costain Senior Project Manager for the Shieldhall Tunnel, was impressed with the piling operation: “The location and size of our site is very challenging but with some careful planning and collaboration with Bachy Soletanche, a major part of this development is now complete and, very importantly, without any issues or incidents.

“It was great to see that final pile being completed and now we are set to begin the next part of the project, when we connect the 150m-long tunnel boring machine and begin tunneling.

“We’d like to thank the Bachy team for all their assistance and look forward to working with them again on future projects.”

The Shieldhall Tunnel will be Scotland’s largest wastewater tunnel, measuring 4.70m in diameter and 3.1 miles long, and will form part of the biggest upgrade of Glasgow’s wastewater network in more than a century. It will run between Craigton Industrial Estate and Queen’s Park, and will resolve water quality and reduce flooding issues at key locations in the area served by the Shieldhall Waste Water Treatment Works.

Work on the project began in October 2014 and is due to be complete in early 2018.

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