CIVIL ENGINEERING AND CONSTRUCTION
Engineers are part way through rebuilding Arnside viaduct to make it a safer and faster part of the rail network. It’s required precision planning, as Network Rail project manager Rhiannon Henshaw explains.
A
rnside Viaduct, built in 1856 to take the Carnforth and Whitehaven line
over the River Kent estuary in Cumbria, has been showing its age.
There has been a deterioration in the superstructure and a long-term speed restriction has been in place for more than ten years, limiting passenger trains to 30mph instead of 60mph and freight trains to 20mph. Network Rail considered a number of minor upgrades to improve its condition, but decided in the end to go for a full £11.1m rebuild of the viaduct, with new decks and track, allowing it to be restored to 60mph and a route availability of RA10, up from RA8 now. Engineers have been on site since the beginning of the year, and started the major phase of the works when the blockade began at the end of March.
RTM caught up with Network Rail project manager Rhiannon Henshaw to discuss the reasons for the works and progress so far.
She said: “It’s a 51-span structure, non- electrifi ed, originally constructed in 1856 from wrought iron, using longitudinal rail girders supporting the jointed bull-head rail via long timbers. It was single-line until 1863 when it was double-tracked.
“It was originally cast-iron framed, then encased in concrete between 1914 and 1916. The only other major refurbishment was in the 1990s when new seating was installed for the long timbers; it’s been deteriorating ever since. That’s why the decision was made to do this.”
Deterioration
“The main drivers for the scheme were the deterioration in the condition of the superstructure, and there was also reduced capacity for heavy axle-weight freight. We are envisioning being able to have more freight cross there after this.
“We’re also trying to get rid of longitudinal timbers; that’s a Network Rail standard. The permanent way was in poor condition as well, and there were corrosion traps that made it very diffi cult to inspect and maintain.
“We’ll be replacing the bull-head rail with continuous welded rail,
Pandrol VIPA base-plates, as we did during the Leven viaduct works six years ago.
“We’ve actually had some complaints from local residents about using CWR, as they will no longer hear the ‘clickety-clack’ when the trains go past, which they liked!”
Some regular passengers even insisted they wanted to keep the 30mph speed restriction in place – as it gave them more time to look at the local wildlife out of the carriage windows as they crossed the viaduct. Arnside station has remained open during the works, albeit with single-line working, but the viaduct itself is subject to a 16-week blockade to allow the works to take place.
When the works are completed, it will improve life for passengers using
supported on
TransPennine and Northern services, as well as the fast-track freight to and from Sellafi eld and elsewhere.
Safety issues
Henshaw told us: “The new deck units will provide derailment protection, something we like to have on all our structures.
“New walkways along the length, both sides, will remove the requirements for carrying out inspections ‘red zone’, which is currently in force; that will reduce costs and planning requirements for the future.
“There’s also a safety issue, because red zone working was only allowed in between certain trains or at night time – going out on the viaduct to do inspections at night, I can’t imagine how bad that must have been.
“It can be such a dangerous environment.”
There are no night works currently taking place as part of the works, but there are options to do so if necessary.
“It’s something we want to stay away from if possible,” Henshaw says. Currently engineers are working on the viaduct from 6am-6pm, six days a week.
Henshaw explained: “We’re installing the walkways fi rst, so we’ve never got an open edge at any time. We removed the existing walkways and installed the new ones before we installed the new decks.”
See overleaf rail technology magazine Apr/May 11 | 55
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