Work to stabilise a railway embankment in south London has just got underway after monitoring identified the structure as being at high risk of collapse.
Network Rail has said that tis engineers have been monitoring the stability of the embankment close to Streatham Common station after regular inspections raised concerns and inclinometers confirmed the ongoing movement.
The year-long stabilisation scheme is part of a £300M government-funded programme to boost the reliability of the railway in the south east, cutting delays and providing a better, more reliable rail service for tens of thousands of passengers each day.
Network Rail route asset manager Derek Butcher said: “The work we’re doing is absolutely vital to keeping Southern and Thameslink trains running safely and reliably for passengers. Streatham is a key location on our railway network and any disruption here has the potential to disrupt services across the whole of south London. We thank people in the area for their patience while we carry out this work.”
According to Butcher the embankment at Streatham South Junction has been showing signs of distress for a number of years with poor track geometry and misalignment of lineside cable routes.
Inclinometer monitoring showed that the movement is continuous through both summer and winter months,” he said. “For this reason, and due to the location supporting the junction of several inner London commuter routes, it has been decided to carry out works to stabilise the slope.”
The work will not be straightforward though due to the presence of two high voltage feeder routes, lineside signalling cables and other trackside infrastructure.
“The main driver for the scheme is the deteriorating track geometry, it was clear that whatever option is chosen to stabilise the slope needed to provided robust support for the track and the lineside cables,” added Butcher. “In addition, for safety reasons, the scheme will provide a flat walkway along the side of the track, allowing track workers somewhere safe to stand and walk.”
The embankment will be stabilised using an anchored bored pile wall formed with 450mm diameter, 10m long piles at 1.35m centres with lateral support provided by raking anchors.
“The temporary works required for the construction are fairly complex, requiring many of the lineside cables and equipment to be moved temporarily away from the line of the piles,” said Butcher. “In addition, a piling platform is required in order to provide access for the plant to the crest of the embankment.
“The piling platform will be constructed from expanded polystyrene blocks, and incorporated into the permanent works using a reinforced earth covering, allowing the embankment to achieve a green finish. The site is located within a residential area, so the aesthetics of the solution were a major consideration in the design.”
The scheme is set to be completed in early 2019.