Piling works have begun by the HS2 contractors on the UK’s longest rail bridge. The foundations will span for the 3.4km-long Colne Valley Viaduct for which approximately 300 piles are being bored to support the viaduct.
The bridge structure will allow carrying the new high-speed rail line across a series of lakes and waterways on the northwest outskirts of London. It will cover almost 1km longer than the Forth Rail Bridge and carry trains expected to travel at speeds of up to 200mph.
HS2’s main works contractor for this section is Align JV – comprising Sir Robert McAlpine, Bouygues, and VolkerFitzpatrick. The design team comprises architect Grimshaw, the engineers Jacobs and Ingerop-Rendel.
The structure will be supported by 56 piers, with spans of up to 80 metres long. It will be carrying the railway around 10 metres above the surface of the lakes, the Grand Union Canal and the River Colne.
The main deck of the viaduct will be built in sections at a temporary factory nearby before being assembled from north to south. The test piling programme has already been completed with engineers sinking 12 piles at two locations.
The testing is done with geological and structural data fed back into the design of the viaduct. According to the reports, the deepest piles are going down 55 metres. This has also resulted in a 10-15% reduction in the depth of the piles and associated time and cost savings.
English 