Hydrofraise drilling machine prepares to excavate 30m diaphragm walls for the Stratford Box on the Channel Tunnel Rail Link.
The Hydrofraise (or Hydromill) is a giant construction machine that can weigh up to 80 tonnes, stands around18 metres high and is a marvel of sophisticated technology. Used to build underground concrete walls (called slurry or diaphram walls) and using onboard computer guidance, it cuts a trench using powerful hydraulic motors and rotating teeth set on twin drums through difficult ground that - when filled with concrete - create retaining walls under the surface. The absence of vibration and shock makes this system very suitable for use on urban sites. This excavation system makes it possible to drill piles panels or diaphragm wall elements in a very wide range of ground, from cohesionless soils to hard rock. The huge Stratford Box on the Channel Tunnel Rail Link (Contract 230) is 1075m x 50m with a depth of 25m to accommodate Stratford International Station and 160km/h crossovers allowing parked trains to accelerate up to the CTRL main line speed of 230km/h. The box has reinforced concrete diaphragm walls thick and the centre section of the box is constructed using cantilever diaphragm walls. The base slab is concrete and acts as a strut to the diaphragm walls. The ‘Box’ is effectively a huge concrete lined trench cut into the native geology. Though the station box has been designed to avoid inundation from the River Lea and other measures are in place to dispose of rainwater, it wasn’t built to resist the uplifting effects of rising groundwater that (in a worst case scenario) might cause the structure to float like a gigantic concrete barge. To avoid such problems, the lower aquifer water level is maintained 10m below the base slab and a permanent de-watering system has been installed using submersible pumps in 22 boreholes drilled 30m into the chalk. The £ billion Channel Tunnel Rail Link (now High Speed One) was built between 1998-2007 and partly funded by the European Union, it forms a section of the Trans European Rail Network.
Size: 2421px × 2421px
Location: Stratford, London, UK.
Photo credit: © qaphotos.com / Alamy / Afripics
License: Licensed
Model Released: No
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