Redi-Rock walling used for rebuild needing speed of installation

In 2015, a 50m section of platform 2 was heavily damaged when loose equipment from a passing freight train smashed into it. The damaged area was closed off and Network Rail design engineer, Alex Evans, took advantage to bring the Victorian stationÂ’s platform up to modern standards, began plans for a rebuild.

With train operating company, Northern Rail (a key stakeholder) expecting to run longer trains through the station from April 2019, the rebuild team had to come up with a solution which could be undertaken at speed. This meant scrapping the initial design by external consultants in favour of a scheme that avoided much of the track possession they had proposed.

“The old design was all possession work. The plans were to excavate down right next to the track and cast a strip footing continuously all the way down,” says Mr Evans. Situated within a 9m deep soil cutting; the original platform of Moston Station was a concrete structure that retained a granular fill. It incorporated an old brick retaining wall at the rear, which used to retain the cutting slope behind it. Network Rail’s in-house civil engineering team were tasked with redesigning and building the area in a short, eight-month programme. Their design and construction method centered on removing the need to use the track for plant.

Mr Evans explained: “Normally, the traditional method of construction would mean transporting material via the railway, this means the railway needs to be closed so working hours are restricted to midweek nights and Saturday evenings, which for this area would mean around six hours per shift. The access pointed for the plant is more than 1.6km away and the speed limit is 8km/h, so once a machine had got onto the railway and made its way to the site, an hour would have been lost. This would have reduced the working time to around four hours per shift.

The new design meant that most of the work could be undertaken while the railway was open, with the new platform construction excavating the toe of the cutting to create room for a new platform and replacing the old brick retaining with a new precast concrete one. Mr Evans added, “There were some possessions for some elements of the work but these activities were achievable in the possession windows, whereas the alternative design was more complicated as it involved significant temporary
work, which posed a risk to track quality and were time-consuming.”

Network Rail overcame the problem of where to place the construction equipment serving the site by undertaking an analysis of the stability of the cuttingÂ’s slope, which showed that it would be stable during construction while the toe was removed and the Marshalls CPM Redi-Rock retaining wall installed.

To find out more please visit https://www.cpm-group.com/news/redi-rock-walling-used-for-rebuild-needing-speed-of-installation/