Station over the Thames - Keltbray at Blackfriars Station

By Lindsay Gale06 February 2013

The Blackfriars Station site from the air - a major challenge for Keltbray

The Blackfriars Station site from the air - a major challenge for Keltbray

The unique inner city environment, working in and around a live, fully operational rail terminal and tube station and the Thames River, imposed huge operational constraints upon the site. Almost all aspects of the work had a major interface with London Underground (LUL), Network Rail (NWR) or other contributing stakeholders such as the Port of London Authorities (PLA).

London Blackfriars Station handles millions of passengers every year. The landmark station will be providing increased interchange between national rail and LUL services and make London's Bankside and South Bank tourist areas much more accessible to passengers. The redeveloped Blackfriars station will be the first in London to span the entire length of the River Thames and will provide improved interchange between rail and tube, and a new station on the South Bank.

Keltbray delivered the demolition package at Blackfriars Station as part of the £350m redevelopment. Working for Balfour Beatty on behalf of NWR, Keltbray were awarded the contract in 2009 as part of the £6bn Thameslink Programme to upgrade the line to increase passenger throughputs and increase service patterns. The NWR Thameslink service remained operational throughout the duration of the works, with the exception of a limited amount of possessions that were utilised for essential works. At the North station, LUL services remained operational throughout within a temporary tunnel while the station was closed to allow total demolition and reconstruction of the underground station.

The redevelopment of Blackfriars station has been a hugely complex engineering challenge. Retained infrastructure both overhead and underneath live operating train tracks carrying both public and freight train stock, and the heavily trafficked Thames below, imposed constraints that required meticulous planning and risk analysis to develop the appropriate methodologies. The works incorporated the demolition at the North and South stations, excavation of a propped basement, and the removal of two large trusses spanning the Thames – all with major rail interface. The project can be summarised across four main work areas.

Four activity areas

First was the north station demolition work, which consisted of the removal of the existing national rail station including the roof, platforms, track structure, abutments and superstructure; the existing LUL ticket hall structure directly over the LUL temporary tunnel; the existing building over the railway - comprising compound plate girders and 200 tonne truss; the brick arch structure over the LUL temporary tunnel; and the existing entrance building adjacent to both LUL and national rail assets.

Demolition at the south station consisted of the phased demolition of the existing viaduct incorporating temporary works along the cut lines and partial demolition of the existing bridge abutment; the salvaging of retained stonework elements; and groundworks including excavation, pile probing and pile breakdown.

Work over the Thames required the removal of two trusses each over 60m (197 ft) long over the river. Excavation work made up the fourth area of activity and this included the excavation of the new basement within a secant piled box to 3 m (9.9 ft) depth below the LUL track; the design and installation of a jacked propping scheme for the new basement, incorporating a temporary bridge and finally, the Installation of a propped temporary ‘king post’ wall to facilitate the piling works, and a specialist structural piling deck to facilitate the piling works.

Working in a live rail environment with multi-disciplinary stakeholders, the Blackfriars project team (led by Anthony Walsh, project director, and Nick Smith, project manager) worked in partnership with Balfour Beatty and Network Rail while satisfying the requirements of Transport for London and the Port of London Authority, to successfully deliver the demolition and ground works elements of the contract within the project milestones and with an excellent safety record.

To this end a fully collaborative culture was adopted by all parties from the start that included a focus on early involvement, establishing common processes and tools, measurement of performance and implementing long term relationships to achieve the vision ‘to deliver the work safely, within programme and within the target cost set out’.

The complex structural and foundation works undertaken to build the first railway station to straddle the Thames in London required Keltbray’s expertise spanning a diverse range of disciplines including demolition & civil engineering, piling, Keltbray Rail, asbestos removal and structural engineering. Keltbray believes that the project provided a clear demonstration of the benefits and synergies that can be delivered by providing a total in-house service.

Blackfriars Station project – key facts

Delivery features
Live and fully operational rail terminal and underground station
Weekend and night possession
Environmental control of noise and vibration
Removal of a 200 tonne truss over a live railway
Lifting out 100 year old trusses spanning 63 m (207 ft) over the river Thames

Project statistics
£13 million (US$20.7 million) contract
2.6 hectare (6.5 acre) site
Completed on time and to budget
Use of PSC certified timber 100%
65,000 tonnes of material removed
95% recycling rate achieved

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