It’s our job to look after the thousands of structures across our network
Many of the bridges, tunnels and viaducts on Britain’s railway are from the Victorian era. Being responsible for this national heritage is both a privilege and a challenge.
We’re proud to look after some of Britain’s most admired and celebrated structures. These include the Forth Rail Bridge, which was the first major structure in Britain to be made of steel, and Brunel’s Box Tunnel, between Chippenham and Bath in Wiltshire, which was the longest railway tunnel ever built at the time of opening.
But the positive aspects of looking after such iconic, historical landmarks are offset by the challenges they present. Some of these structures are very old, so are vulnerable to extreme weather conditions and often need to be renewed. They may also need to be reconstructed; many bridges aren’t high enough to fit the overhead electrical equipment that’s required to power electric trains.
Fixing and futureproofing our infrastructure
Our asset teams monitor our 40,000 bridges, tunnels and viaducts, checking structural aspects, assessing whether they can accommodate new electric trains and those carrying freight. They also carry out repairs as required.
Some of our recent works
We carried out an intensive seven-week engineering project to repair the Victorian-built Lamington Viaduct, which carries the West Coast Mainline over the River Clyde, after flood damage severely weakened its structure.
We completed a £17m project in Cheshire to protect the county’s most iconic railway bridges and viaducts from the weather for decades to come, including repairs to brickwork by waterproofing it and removing water stains.
We’ve upgraded the 130-year-old Severn Tunnel ready for electrification of the South Wales Mainline. Our work included removing four-and-a-half tonnes of soot from the tunnel and making sure the existing brickwork was secure before drilling the thousands of holes needed for the specialist overhead line equipment.
In 2016 we completed the upgrade of Farnworth Tunnel near Bolton to accommodate two electrified lines, and completed a £60m project to refurbish and upgrade the kilometre-long Glasgow Queen Street Tunnel as part of the ScotRail Alliance.
Increase in demand for rail freight means we need to make sure our network can accommodate more of the wider, taller and heavier freight trains. In the south west, we lowered approximately one mile of track at Dundas Aqueduct so that the line could be used as a diversionary route for taller freight trains in the future.
Innovation: Avoiding bridge reconstruction
Overhead line equipment has to be installed to electrify the railway. This usually means there needs to be a greater distance between the railway and any bridges above it so the overhead equipment fits beneath the bridge. Typically, the methods to create this extra headroom are either lowering the track or demolishing the bridge arch and replacing it with a precast concrete unit.
Where possible we avoid reconstructing bridges, as it’s usually the most costly option and can disrupt both the road and rail network. It can be the best choice, if a bridge is in poor condition, but technical alternatives can provide solutions that avoid this costly reconstruction.
The Rail Safety and Standards Board (RSSB) teamed up with Network Rail and the Department for Transport to try to find potential innovative solutions.
RSSB, Network Rail and the Department for Transport launched the Avoidance of Bridge Reconstruction competition in February 2014 as a co-funded innovation-based project. Its aim was to find solutions to increase the clearance beneath masonry arch bridges without the need to rebuild these structures.
The competition was open to all industry. Of 11 submissions, nine were funded through phase 1 (feasibility study) and four won funding for the phase 2 full-scale demonstrator project off the live rail network. This stage was needed to confirm that any technical design assumptions were valid, and to prove the methods and equipment worked correctly.
ElevArch jacking technique
One of the proposals that made it to this final stage was from Freyssinet and Bill Harvey Associates, who developed the bridge-jacking solution ElevArch, which now has UK and international patents and has won numerous industry awards (see below).
The demonstrator took place in autumn 2016 on a bridge at Moco Farm near Winslow, Buckinghamshire. The segmental arch design dates from 1850 on the mothballed Bicester-Bletchley line, which will be part of East West Rail phase 2. The bridge is 4.3m wide with a 10.1m span, and was designed by renowned civil and mechanical engineer Robert Stephenson.
Bridge-jacking is a technique usually used for bridges with a flat-deck span made of steel or concrete, so this was the first time in the world it had been attempted on a masonry arch bridge.
The benefits of ElevArch over the typical methods of track lowering and bridge reconstruction include significantly reduced costs, shorter and reduced numbers of possessions needed to carry out the work, and the reduced environmental impact – the structure is also retained, improving the heritage value.
Watch the video below to find out more about the ElevArch technique and demonstrator.
The ElevArch method used on the Moco Farm bridge has since won a number of awards:
- Vinci Innovation Grand Prize – September 2017
- Railway Industry Innovation Awards 2017 – June 2017
- Structural Awards 2017: Outstanding Value – November 2017
Pictures 1 and 2: The ElevArch process in progress
Picture 3: The bridge at Moco Farm prior to the bridge-jacking
Picture 4: The bridge after the ElevArch process
Case study: Ordsall Chord bridge replacement (timelapse)
This timelapse video below shows the removal of the old bridge at Water Street and the installation of two new bridges to support the connection of the Ordsall Chord in Manchester, part of the Network Rail Christmas works 2016.