The sight of a new piling rig in east Manchester has signalled the start of major construction work on Greater Manchester’s Metrolink expansion.
The rig is being used to create the concrete retaining walls of an underpass which trams will use to run beneath Great Ancoats Street on the new Metrolink line to Droylsden.
It is the first major piece of engineering work to take place in a £600M Metrolink expansion project, which will also take trams on new lines to south Manchester, Oldham and Rochdale, and MediaCityUK in Salford.
Over the course of the work on the underpass MPact-Thales – the consortium appointed to design, build and maintain the new lines – will move up to 20Ml of soil.
The walls will be constructed using more than 400 concrete piles, ranging in diameter from 90cm to 1.5m, set 15m deep. The piled walls forming the retaining structures to the Great Ancoats Street underpass are being installed using the continuous flight auger (CFA) technique.
The system involves a hollow-stemmed continuous flight auger being rotated into the ground to the required depth. As the auger is withdrawn, plasticised concrete is pumped down the hollow stem under balancing pressure, forming a shaft of liquid concrete to ground level, maintaining support to the sides of the shaft.
A reinforcing cage is then inserted by hand or vibrator. The cage is provided with welded spacers, which centralise it within the pile bore, and the cage is secured at the required top level.
Bryan Diggins, project director, MPact-Thales, said: ‘The method of piling that we are using creates significantly less noise, dust and vibration than the alternatives. ‘We’re also looking into ways to recycle the spoil material so there are fewer lorry movements in the area.’
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