UNITED KINGDOM About Contact Choose website HOME SERVICES & SECTORS PROJECTS WORLDWIDE NEWS & EVENTS CAREERS United Kingdom Projects Bermondsey Dive Under | Project data Client: Network Rail Completion: December 2017 Value: Approx £60m Construction: Main contractor Skanska Services we provided Rail engineering The team Will Duckett Tim Holmes BERMONDSEY DIVE UNDER London, UK Bermondsey Dive Under is a key component of the final stage of the Thameslink project to rebuild London Bridge station. It is a new section of railway track and infrastructure that allows Thameslink lines to cross the Kent lines unimpeded on the eastern approach to London Bridge. Value engineering and detailed design by Ramboll, in collaboration with main contractor, Skanska, and Network Rail, have delivered significant cost benefits. Rebuilding for the Thameslink programme First opened in the 1980s, Thameslink delivers a north-south main-line rail link through the heart of London. Upgrading it is a massive undertaking. The £6bn engineering project is a third of the cost of Crossrail’s east-west rail-link, but it will transform the existing cross-capital route into an equally significant part of the southeast of England's railway infrastructure. The existing railway formation at the Bermondsey site comprises 11 tracks on elevated Victorian masonry arch viaduct structures. Rebuilding work is crucial to enable Network Rail to achieve its objective of allowing 24 trains to pass per hour through the Thameslink core. Putting it simply, the dive under project involves untangling the old track on the approaches to London Bridge. To support the new Thameslink lines, the project scope also includes crucial strengthening of numerous metallic bridges on the approaches to London Bridge. The Dive-Under The dive-under involves the design of a new grade separated junction at Bermondsey to minimise conflicting crossings on the eastern approach to London Bridge Station. This will be formed by a series of new structures constructed along the line of existing operational railway viaducts. Wherever possible, existing structures are being reused to reduce disruption and waste. The new structures carry two fast lines over four other lines lowered underneath. All these lines pass over a new underpass that improves pedestrian access to Millwall Football Club. Ramboll’s contribution Ramboll and Skanska were appointed to undertake the outline design, detailed design and implementation of the strengthening works to existing structures and to design the Bermondsey Dive Under. The new structures include earth embankments, reinforced earth, pre-cast arch viaducts, steel composite bridge structures, concrete box structures and reinforced concrete integral bridges. Within the Structural Strengthening part of the project a total of 52 structures were identified and it is envisaged that 18 of them will require strengthening. Our approach “The key technical challenges for this project are to develop designs that minimise disruption to the live railway, de-risk the blockades and coordinate with the existing structures.” Will Duckett, Ramboll project manager. Ramboll’s key innovation on this project was to propose a pre-cast arch solution as an alternative to the solution developed during the outline design stage, which was for reinforced in-situ concrete portals. This proposal is in some respects novel as it is uncommon for new railway structures to be designed as arch structures. On the other hand it is using a structural form that has been used often since Roman times. Reduced number of piles One of the major features of the arch structure proposal is the similar form of the new arches compared to the existing masonry arches. This ensured the load distribution on the foundations remained relatively unchanged, allowing for many of the existing piers to be reused, this contributed significantly to reducing the number of piles. Optimised designs also meant that the same piling rigs could be used throughout the project. The Pre-cast arches The pre-cast arch design was developed with a constant arch radius to maximise repeatability and to allow off site manufacture, thereby de-risking material supply during the blockade, reducing site safety risks and allowing key elements to be prefabricated. This solution also reduces the long term maintenance requirements as expansion joints are eliminated and the concrete arch structures are in compression. The concrete arch segments were designed to have a similar stiffness to conventional masonry arch rings. They have concrete backing with a curved upper profile, as typical arches, and then filled with modern foamed concrete material. Careful thought was required regarding the thermal performance of the fill material so that the arches behave in a similar fashion to long lengths of masonry arch viaducts that breathe under thermal loading. The Brick facing will give long term protection to the foamed concrete and provide an aesthetically pleasing finish. Project benefits Network Rail said the redevelopment work at Bermondsey will make London Bridge station more accessible, reduce congestion and increase passenger capacity by 50%. Over the whole route, peak train frequency will increase from the original 7-8 minutes, to four minutes currently, and 2-3 minutes by the end of the decade. Multiple regional destinations on either side of the capital will be connected for the first time with a direct rail service through London with Tube-like service frequency. The current Brighton-to-Bedford route will add Cambridge, King's Lynn, Ashford and Eastbourne as destinations. The line upgrade has also acted as a catalyst for urban regeneration, linking many major commercial redevelopments in the capital, such as at Elephant and Castle in the south, and Brent Cross to the north. Related news WW1 ticket hall uncovered Described as ‘ghostly’ the platform structures at track level are the remains of Southwark Park station Will Duckett Project Director T +44 (0)23 8081 7500 E will.duckett@ramboll.co.uk © Ramboll UK Limited Company registration +44 (0)20 7631 5291 london@ramboll.co.uk Sitemap Cookies & disclaimer Contact