HS2 Ltd has unveiled designs for the first of three “green tunnels” that will be built on Phase One of the 225km high-speed line between London and Birmingham and the West Midlands.
The modular design is set to reduce carbon levels during construction by 50%, with the tunnel structures built away from site.
Manufacturing of segments for the 2.4km Greatworth tunnel is underway in Derbyshire and will be transported to the Northamptonshire site where the structure will be built over the new line. Once assembled it will then be covered by earth and landscaped to fit into the surrounding countryside. Similar to techniques used when constructing French high-speed lines, the approach has been developed by HS2’s main works contractor EFKB, a joint venture of Eiffage, Kier, Ferrovial Construction and Bam Nuttall.
The tunnel has been designed an m-shaped double arch and will have two bores. Five different concrete pre-cast segments will be slotted together to create the double arch, one central pier, two side walls and two roof slabs. All 5400 segments for the Greatworth tunnel will be steel reinforced with the largest weighing 43 tonnes. The tunnel will also have porous portals at each end which are designed to reduce the noise of trains entering and exiting the structure.
Similar structures will be built near Wendover in Buckinghamshire and Chipping Warden in Northamptonshire. Combined, these tunnels will be 6.4km long. In total there will be 13,290 segments manufactured for the three tunnels.
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