Bletchley Flyover - EWR Alliance
Project Details
Project -East West Rail 2 - Bletchley Flyover
Sector - Infrastructure
Technology - Concrete
Project Overview:
Bletchley Flyover (BFO) is one of the most complex engineering challenges on East West Rail Phase 2. To ensure the structure – originally opened in 1959 - meets modern standards and allow rail services to cross over the West Coast Main Line (WCML), East West Rail Alliance (EWRA) developed an approach embracing offsite construction, enabling the flyover to be dismantled and rebuilt whilst maintaining the operation of the WCML, minimising disruption, saving six months and providing a £70m saving.
The 605m BFO forms a key part of the East West Rail project and will enable new rail services to cross over the West Coast Main Line (WCML) when the project enters into service in 2025. In order for the structure to meet modern rail specifications and to increase the structure’s lifespan from 60 to 120 years, following extensive surveying, the East West Rail Alliance (EWRA) recognised that sections of the structure spanning the WCML and Buckingham Road would need to be dismantled and rebuilt. However, this would need to be achieved whilst maintaining operation and minimising passenger disruption on the WCML – one of the busiest railways in Europe.
Committed to driving innovation and delivering value for money, EWRA, comprising Atkins, Laing O’Rourke, Network Rail and VolkerRail, worked collaboratively to embrace innovation and develop a strategy and an engineering solution that would allow the project to be delivered without impacting the WCML whilst also meeting the programme demands of the wider EWR2 project.
Constructing the new Bletchley Flyover in a traditional manner would have involved the use of in situ concrete and extensive temporary works, requiring substantial materials, planning, resources and transportation and consuming considerable programme time. A traditional approach would also require lengthy and expensive closures of the WCML. In response to the challenge, EWRA explored the partner’s best practice and - working collaboratively - the team developed LOR’s Design for Manufacture and Assembly (DfMA) precast concrete shell abutment solution to build a new box bridge over the WCML. Manufactured at LOR’s Centre of Excellence for Modern Construction, the precast concrete shells can be stacked to form bridge abutments, retaining walls and piers in various heights and widths. Self-standing, the shells act as permanent formwork for in situ reinforced concrete within the cellular void, largely eliminating time-consuming conventional temporary works and shuttering.
In total, 138 2m high and 1.75m deep shell abutments were used to build the new flyover’s 85m box bridge support structure across the WCML, without impacting local residents, rail services or disrupting passengers. Once the bridge abutments were constructed, 103 precast concrete beams were lifted into place above the WCML over a planned closure during the early May Bank Holiday weekend in 2021. Thanks to the offsite approach and its successful delivery, the structure was handed over on schedule to the EWRA track team to begin their works in October 2021, saving 6- months on programme and providing a £70m saving.
