Scottish Water’s 5km long Shieldhall Tunnel, in the south of Glasgow, passed a significant milestone yesterday when the Herrenknecht TBM being driven by contractor – the Glasgow Tunnel Partnership, a joint venture of Costain and VINCI Construction Grands Projets – reached the half way point under Pollok Park.
The £100M, 4.7m diameter tunnel will enable Scottish Water to improve water quality in the River Clyde and tackle flooding. Tunnelling started last July and is expected to complete later this year.
Paul Kerr, Scottish Water’s capital investment general manager, said: “We are delighted to have reached this milestone half-way stage in the tunnel construction.
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“The Shieldhall Tunnel team includes some of the best and most experienced tunnellers in the world and they are making great progress with what is the biggest project of its type Scottish Water has ever undertaken.”
The TBM is tunnelling at a speed of about 2mm per minute, with a cutting wheel equipped with 25 cutters at the front, through challenging ground conditions which includes boulders, clay, hard sandstone, glacial tills and old coal workings.
The first half of the tunnel construction has taken it under Bellahouston Park, the Glasgow Paisley Canal railway line and the M77.
As it inches its way along the route, preparatory work is progressing at Queens Park where, in the past few days, work has been continuing on the construction of an exit shaft for the TBM and a smaller tunnel from that shaft to another shaft which will use a newly-installed flume to connect the tunnel to the existing network.
The route of the tunnel was chosen to maximise the use of parkland and minimise disruption.
The tunnel is a key part of Scottish Water’s £250M, five-year programme of work, launched in 2013, to improve river water quality and the natural environment.
The programme is the biggest investment in the Greater Glasgow area’s waste water infrastructure in more than a century.
In reached the half-way stage, works have produced some interesting stats:
- More than 1600 concrete rings of the tunnel (which are 1.5m-long) have been completed – each made up of six pre-cast concrete segments weighing 2.5 tonnes
- More than 150,000 tonnes of earth, stone, clay and other aggregates has been excavated.
- More than one million man hours of work have been completed on its construction
- More than 90% of the excavated material will be recycled.
- More than 12km of pipes have been installed in the first half of the tunnel to service the TBM with air and water.