Crossing the Colne Valley
700-tonne machine begins deck construction on the UK’s longest railway bridge.
DECK segments for what will become the UK’s longest railway bridge are being lifted into place by a 700-tonne launching girder.
The machine began work at the end of May on the Colne Valley Viaduct, which will carry the HS2 route for more than two miles – across lakes, the River Colne and the Grand Union Canal – between Hillingdon in West London and the M25.
The 160metre-long (525 feet) launching girder, which was made in 2004 for use in the construction of Hong Kong’s East Tsing Yi Viaduct, is the only one of its kind in the UK. It will move from one pier to the next, lifting the deck segments into place, one each side of the pier, to balance the structure and create two half-arches simultaneously.
HS2 Minister Andrew Stephenson, who attended an event to mark the beginning of the deck-building work, described it as “a landmark moment for HS2 and a feat of British engineering”.
In total, 1000 deck segments (which are being manufactured at a temporary plant on-site, close to the bridge’s north abutment) will be used, individually weighing up to
140 tonnes and each varying slightly in shape due to the curve of the viaduct as it crosses the valley.
Some of the spans of the viaduct, which will be
10 metres (33 feet) above the water, are 80 metres (262 feet) long. Working ahead of the girder, 56 piers for the viaduct, each weighing around 370 tonnes, are being constructed.
Four jetties (three of which have so far been completed) will be used to position construction equipment.
Where piles are being bored directly into the lakebed, a cofferdam is used to hold back the water.