Teams at the halfway point on the viaduct

Align teams are celebrating the halfway point in the construction of the Colne Valley Viaduct, a major milestone in the HS2 project, which will improve mobility in the UK. In total, around 1.7 kilometre of 3.4km viaduct has now been completed that will make this the longest railway bridge in the UK.

The viaduct near Denham (Buckinghamshire) – one of HS2’s landmark structures – will carry high speed trains at speeds of up to 200mph out of London, across the Colne Valley and the Chiltern Tunnel.

Construction of its 56 piers to carry the deck across both land and water began in December 2021. The CVV team completed the last concrete pour for the final V-pier on the viaduct. This is a huge achievement considering the complexity of these piers and the requirements to work at height, over water and in an environmentally sensitive area. The V-piers – each weighting in at 1,800 tonnes - are designed to support a row of elegant arches inspired by the architect to represent the flight of a stone skimming across the surface of the water.   

For the past 18 months the massive launching girder Dominique has been working its way south across the valley, one pier to the next, to lower and fix into place the viaduct’s deck segments. Weighing up to 140 tonnes each, more than 500 of the Colne Valley Viaduct's 1,000 deck segments have been installed. Each one is uniquely shaped to enable the structure to gently curve as it carries the railway. 

October 2023, a record-breaking month for the TBMs

Both TBMs Florence and Cecilia are continuing to make great progress on their drives under the Chilterns, with Florence currently at 14.1km and Cecilia not far behind at 13.8km. During one week in October, Florence set a record for the project advancing 232m, and for the month as a whole Florence achieved another record advancing 842m. Combined with Cecilia, the TBMs advanced a total of 1,562m in October, with the invert slab concrete teams matching their progress.    

The tunnel precast factory supplied the 5,467 segments required and has now manufactured well over 90% of the segments required to complete both tunnels. Over 2.7million m3 of chalk cake excavated from the tunnels has now been laid and landscaped at the South Portal, which will eventually create a unique chalk grassland.

Meanwhile, the cross-passage team, constructing 38 cross passages and also one adit at each shaft, is also making great progress with the mining completed on 19 cross passages and 2 adit, so they are over 50% complete. The shafts team has also completed a number of enormous concrete pours, including 869m3 at the North Portal.