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The largest below-ground rail crossover on the London Underground network

Category: General / 31 May 2019

The Northern Line Extension (NLE) team has successfully completed installation of the rail crossover at Battersea Power Station.

The NLE team at Battersea have successfully installed a 147m crossover, which forms the final piece of the NLE rail track. The entire extension is now connected by rail from end to end in both tunnels. The new low vibration track (LVT) runs from the overrun tunnels at the western end of the Battersea Power station site all the way through Nine Elms station to the step plate junctions (SPJs) at Kennington, where the extension links into the existing Northern line. All in all, 5.8 kms of rail track have been installed.

The crossover rail track was fabricated, for the Ferrovial Agroman Laing O’Rourke JV (FLO), by Progress Rail, in Derbyshire. In September 2018, the rail team undertook factory inspection of the crossover’s individual components. The whole crossover was trial-assembled, surveyed and inspected. All components were then numbered and marked to allow the jigsaw to be put back together again once on site at Battersea.

The individual components were delivered to the NLE Battersea Power Station site in the first week of October 2018, so that they could be lifted down and stored at track level before the reduction in the structural openings of the new Battersea Power station. Installation of the crossover started on site in the first week of April 2019, as planned; once the structural works of the station were sufficiently complete for the track installation to go ahead.

The track in the crossover is formed of 68 bespoke pieces of running rail mounted on 1172 individual LVT blocks alongside 36 conductor rails, all of which must be aligned to meet a stringent set of tolerances. These tolerances include a variation in horizontal and vertical alignment of +/- 3mm of every piece to meet London Underground Limited (LUL) standards. It is a testament to the exceptional team performance to have installed a crossover of this size with no exceedances or variances identified.

When concreting in the crossover track, the team first suspended the track above ground using a set of jigs to provide the accuracy and reliability required. These are modelled on those used to construct the running tunnel section track. Due to the pre-curved and varying profile of the crossover pieces, 72 unique jigs were manufactured. Learning from the installation of other slab track crossovers, several bespoke mechanisms were also developed to prevent common variances that usually require rectification following concreting.

Once suspended and aligned to design, the track was concreted in. Upwards of 800m3 of concrete forms the track bed around the crossover. The installation of the crossover also involved the track team’s largest single pour of 160m3 in one day, which was undertaken in one pour to minimise joints.

Following 7 concrete pours to set the track and trackbed, FLO’s team undertook installation of conductor rail and a total of 88 aluminothermic welds, as well as installation of 4 new Surelock electric points machines. These operate with the signalling system to throw and set the route for trains through the crossover.

Luis Rallo, FLO Deputy Project Director, said “This is a fantastic milestone for the NLE team with the extension now connected by rail to the existing Northern line. Our rail team have demonstrated exceptional workmanship, fantastic progress, exemplary safety and quality standards throughout the entire installation process. The project has welcomed collaboration with Laing O’Rourke and brings together the best practices, engineering and labour resources from the wider Ferrovial group. Additionally, our partner has been paramount for the success of these works and I am now looking forward to the use of engineering trains through the entire extension, which will lead to further efficiencies.”

The completion of the Battersea crossover is the cherry on the cake for this hardworking rail team, which has demonstrated exceptional workmanship throughout the entire rail installation process.

 

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