Last week I attended the first Institution of Civil Engineers (ICE) Essex Branch lecture of the 2014/15 session at Anglia Ruskin University (ARU) in Chelmsford. The subject was the Dawlish Railway Repairs and a very interesting and informative lecture was given bu Emma Lewis of Network Rail and Jon Powell of consulting Engineers Tony Gee and Partners (TGP)
The repairs were necessary after the winter storms of February 2014 washed a significant length of sea wall away and the ground behind supporting the railway leaving the tracks suspended in mid air. The associated rain also damaged the cliffs badly causing a number of landslips which also affected the railway. The damage disconnected areas south of Dawlish from the remaining rail network of the UK.
The storms and the damage were big news and widely covered by the media at the time and there was an obvious need to re-open the railway as soon as possible. Visits by high profile political figures – including the Prime Minister – reinforced this and Network Rail had to develop a plan and a team to get the railway open as soon as physically possible whilst ensuring the safety of all those involved both in doing the work and living in the proximity.
The video included below (not from the presentation) clearly shows the ferocity of the storm and the damage it caused!
Emma kicked off the lecture and described the damage caused to the the railway and its surroundings. She described the challenges Network Rail faced – including re-opening the railway as soon as possible, working safely, ensuring the repairs didn’t get washed away whilst being carried out plus many more. She went on to describe not only the major risks in the design and construction but also some of the opportunities.
Emma covered priorities, programme and cost before describing the team of specialist companies that were assembled at very should notice. Principlle members of the team were:
- Network Rail Initial Management & appointment, Comms, signals, power, track
- BAM Nuttall: Principal Contractor – Dawlish Warren to Dawlish Station. 350m Splash wall reconstruction. Overall co-ordination. Void grouting (BAM Ritchies)
- AMCO: ‘Hole’ reconstruction, cutting failure
- Dyer & Butler: Principle Contractor – Woodlands 200m splash wall, 120m walkway and beach access ramps
- Sisk: Dawlish Station repairs
- Tony Gee: Design and verification
One of the key considerations and risks described by Emma was protecting the ongoing repair works from damage – especially as another storm was forecast for 10 days after the first. A unique and very simple solution was developed for this. A larger number of shipping containers were obtained and lined up on the beach to provide some protection from the force of the waves. These containers were then filled with rubble from the works. You would think this would be enough – and it did protect the works, however the containers were seen to bounce regularly from the force of the waves and their condition afterwards was less than perfect.
Jon then took over the presentation and described the various elements of the works and the design and construction solutions adopted.
The major part of the works was the repair of the 350 metre long section where the sea wall had collapsed and the railway formation had been washed away. Jon described the solution as shown in the section below Click to open larger version in new window.
A robust and simple/fast to construct solution was developed. The lower section of repair was basically layers of concrete fill with each layer restrained by a ‘permanent shutter’ formed from VCBs tied back with tie bars. VCBs (Vehicle Control Barriers) are normally used as barriers through roadworks but they provided a simple and quick to procure solution.
Precast concrete L shaped retaining wall units where designed and installed to retain the road behind the railway on one side and to provide a splash wall on the sea side to form the railway corridor. Once complete the track ballast and rails/sleepers were installed and voila. In practice there was a lot more to it than that but you get the idea.
The timelapse video below (not from the presentation) shows the main works described above:
The video below (not from the presentation) shows views over the works when the retaining wall units were being installed – taken from the ‘orange hornet’ RV.
The other main element of works that was needed only came to light after the repair to the breach had been started and after Network Rail had confirmed when they planned to re-open the railway. This work was to stabilise/remove a significant slip of the cliffs at Dawlish Warren. Jon described the issues they faced and the eventual solution that was adopted – essentially using water cannon to wash all the remaining loose slip material down and into the sea. The Environment Agency allowed them to do this as a special case.
The video below (not the the presentation) shows the water cannon in use – again taken from the RV.
Emma and Jon described the other works including footway reinstatement and works to the station platforms before summing up the presentation. It was incredible to note that the railway was reopened only 8 weeks after the original storm and 2 weeks ahead of schedule – testament to what the construction industry can do. Whilst disruptive to the travelling public and locals in the vicinity, the damage and subsequent repair put civil engineers very much in the public eye and the profile of the profession has definately been raised by the success of the works.
Essex Branch Chairman David Goodliff fielded a number of questions from the audience before thanking Emma and Jon for presenting – especially as they had both travelled from Gloucestershire to speak.