Increasing capacity on the East Coast Main Line with a pioneering new tunnel
As part of our £1.2billion East Coast Upgrade, we’re increasing capacity for passenger trains on the East Coast Main Line by building a new two-track railway line that dives under the line at Werrington, north of Peterborough.
The fly through video below visualises how the new dive under will look when in operation.
The project has several phases and associated key milestones. The first milestone,Stamford Slews, relocated the two Stamford Lines approximately 30 metres to the west, creating the space neededbetween the Stamford Lines and the East Coast Main Line to allow construction of the southern dive under ramp.
This phase of works was completed in early January 2020, with the critical disruptive works taking place over Christmas 2019. Works included 3,580m of new track, associated overhead lines, signalling and telecoms as well as a significant number of enabling stages.
Cock Lane Footbridge
Cock Lane Footbridge is replaced with a wider bridge to accommodate the future position of the re-aligned Stamford Lines. The new footbridge includes ramps to make it compliant with the Equality Act 2010. The footbridge opened in November 2019.
Brook Drain River
Almost 1km of the Brook Drain river had to be diverted to create enough room for the lines to and from Stamford to be moved across. The newly aligned river was designed to help with local flooding issues and features riffles – shallow sections of water – and side pools, where aquatic wildlife can take refuge during storm surges. Existing vegetation was transferred to help maintain a habitat for the rare Four Spotted moth on the riverbank.
A further 500m section of Brook Drain river south of the new footbridge, also had to be diverted.
This location was constrained as it runs parallel to 132kV overhead power lines and a large commercial estate. The solution designed specifically for this location enabled the new Stamford Lines to sit on top of a concrete box culvert cast in-situ, which carries the relocated river.
Diversion of Hurn Road
The position of the old Hurn Road clashed with the proposed route of the new dive-under Lines. In order to progress works, the project worked closely with Peterborough City Council to agree a new route for Hurn Road, which would make way for the new dive-under Lines, whilst continuing to provide access and egress to the properties along the old Hurn Road. The work to Hurn Road was completed in late 2019, allowing construction of the north dive under ramp to continue.
Temporary Lincoln Road Footbridge
A temporary 61 metre footbridge has been installed alongside the existing Lincoln Road Bridge.
This temporary structure, installed in late Autumn of 2019, will allow users of the existing bridge, including a number of utilities, to be temporarily diverted across the new structure.
Whilst the temporary Lincoln Road Bridge is used, work will be able to commence with installing an additional span to the existing Lincoln Road Bridge, which will allow the new Dive-under Lines to run underneath it. Once complete, all users will be able to use the extended existing bridge again.
Milestones in progress
Despite national lockdowns due to COVID-19, we have progressed well. Changes to working procedures and processes, as well as some innovative thinking has allowed our colleagues to continue to work safely throughout lockdowns.
Lincoln Road Bridge
Whilst the temporary Lincoln Road Bridge is in use, we have continued work on the installation of an additional span to the existing Lincoln Road Bridge, which will allow the new dive-under lines to run underneath it.
All the necessary piling has been completed and the new bridge beams swung into place; services are in the process of being diverted into their final position. Once all work on the existing Lincoln Road Bridge is complete, the temporary bridge will be removed and the newly-extended bridge will be open to pedestrians, cyclists and horse riders.
The north ramp has been constructed by installing 183 x 18 metre-long, 900mm diameter, rotary bored contiguous piles and over 900 x eight to 10 metre-long soil nails, finished with sprayed concrete facing. In total 120,000m3 of soil and clay has been excavated to create one of two 940 metre ramps. Final fit out of the north ramp commenced following the ‘curved box’ structure being pushed in to position in January 2021.
In February 2020, our tunnel boring machine, named ‘Chloe and Georgia Whiteman’ after the daughters of Mark Whiteman, a colleague, who tragically passed away unexpectedly in 2019, was launched into the ground to begin the work of boring two three and a half metre diameter, 168-metre-long guide tunnels underneath the operational railway.
Thanks to the state-of-the-art remote track monitoring equipment which constantly measured the position of tracks, tunnelling was successfully completed, unnoticed by the trains passing above, at the start of August 2020.
The tunnels were fitted out with the required slide and guide plates inside to support the pushing of the ‘curved box’ into position under the East Coast Main Line.
South Ramp and South Dive Under Entrance
Mirroring the north ramp, a second 940 metre ramp is being constructed to the south of the dive-under, in the enlarged area made by the slewing of the Stamford Lines.
The Reception Pit, which was used to receive and recover the tunnel boring machine from the ground, was completed in April 2020. Work included the installation of 66 x 18-meter-long bored contiguous piles and the excavation of over 2,000m3 of soil and clay.
Piling for the South Ramp was completed in August 2020, which has now allowed excavation of the ramps to commence. The South Ramp consists of 693no. 900mm diameter, bored contiguous piles up to 18m in length, and a further 340 metres of 10 metre sheet piles.
Bringing the Stamford Lines work forward has enabled the South Ramp to be constructed with no impact to the operational railway or passengers.
From March 2020 work began to build the dive-under structure.
The ‘curved box’ was built next to the East Coast Main Line in nine, interconnected sections. The structure is 155m long, 9.5m wide and 5.1m high, with 1m thick walls and soffit.
It weighs just over 11,000 tonnes, which is 1,000 tonnes heavier than the Eiffel Tower!
The ‘curved box’ was pushed under the East Coast Main Line using large jacks to propel and steer it during January 2021. A trial push took place in December 2020, when the box was pushed forwardby 16 metres to allow the structure to be weighed, the centre of gravity to be identified and all equipment to be calibrated and checked.
Over Christmas 2020, a bespoke signalling solution was installed and tested on the two ‘Stamford’ tracks running alongside the construction site. This work enabled a partial train service to continue to run on the East Coast Main Line while the tunnel was being pushed into place in January 2021.
During a nine-day partial closure of the East Coast Main Line in January 2021, the 11,000 tonne, 155-metre curved concrete box tunnel was pushed into place.
Time-lapse footage below shows the 11,000 tonne curved concrete box being pushed under the East Coast Main Line.
Whilst hydraulic jacks at the rear pushed the tunnel portal forwards at just 150cm per hour, excavators at the front broke away the guide tunnels to reveal the glide plates to guide and steer the tunnel into position.