A 'major' milestone has been reached in a £85m tunnel construction project in Glasgow.

The Costain-Vinci Construction Grands Projets Joint Venture (JV) is developing the Shieldhall Tunnel for Scottish Water.

Geotechnical specialists Bachy Soletanche has now installed the project's 675 piles over a three-and-a-half month period.

The piles play a role in preparing the ground for the tunnel drive stage of the project.

Cased secant piles (CSP) were developed by Bachy Soletanche for the first shaft of the funnel, the service chamber and tunnel boring machine launch chamber.

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In addition, 400m of continuous flight auger (CFA) contiguous piled walls were built 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

Machinery used on the works, including two 25m-tall piling rigs and a 100 tonne CSP had to work in a confined space due to the project site being located in a residential area.

Brian Walker, Costain Senior Project Manager for the Shieldhall Tunnel, said: "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."

The Shieldhall Tunnel will be Scotland's largest wastewater tunnel and will form part of the biggest upgrade of Glasgow's wastewater network in more than a century.

(LM/MH)