Cementation Foundations Skanska has won another major contract under London Underground’s track stabilisation programme. Valued at over £2m, this latest award is to restore ageing Piccadilly line embankments between Boston Manor and Osterley Stations in West London.
A key feature on this project will be the CemRailBeamâ, Cementation’s own (patent in application) reinforced capping beam system. This has been specifically designed to repair failing rail embankments and developed from experience gained on more than 20 projects over recent years restoring the tube’s network of earth structures dating back to the Victorian era.
The high-speed technique overcomes safety, quality and production snags traditionally encountered when casting beams in a confined trackside locations. Now high-precision interlocking precast shuttering units are factory made and rapidly assembled onsite over the piling. Steel reinforcement is then inserted and concrete poured in to form a continuous trackside retaining wall.
Developed as part of an M4I demonstration project, it has been successfully applied in recent projects for LUL and Railtrack, including part of the Central Line, on the main freight line between London and the Channel Tunnel in Kent, and on the East Coast Main Line in North Yorkshire.
Now, just outside Boston Manor tube station, Cementation is repairing over 500 metres of embankment, which have needed increasing maintenance since the line opened in 1883. When completed at the turn of the year, the improvements will enable speed restrictions to be lifted.
The contract awarded by Infraco JNP Limited, a subsidiary of LUL, involves the design and construction of track-level capping beams on a mini-piled base, together with toe walls at the foot of 10 metre embankments on both sides of the line, plus earthworks and track monitoring.
The work, which also covers creating site access, clearing vegetation and replanting afterwards, is being carried out on a partnering basis with Mott MacDonald and Joywheel as key sub-contractors.
More than 670 mini piles will be installed at the crest and base of the embankments. With the line crossing both the M4 and the Grand Union Canal at this point, Cementation Foundations must create three separate access roads totaling some 2.5 kilometres, over playing fields, allotments and a golf course. Because of these complexities Cementation Foundations has been working with the client on identifying and developing suitable design solutions and access routes since November last year which will ultimately reduce risks for all parties.