End of the (East London) Line: Bachy Soletanche nears completion of groundwork scheme
With 20 locations, 28 structures and over two years on site, leading ground engineering experts, Bachy Soletanche Limited is nearing the end of one of its most varied and challenging projects to date; the East London Line Regeneration.
The multi-million pound piling contract was awarded to Bachy Soletanche by main contractor, Balfour Beatty Carillion Joint Venture (BBCJV) in March 2007 for the design and construction of all the piled foundations across Phase 1 of the Project. The works form part of Transport for London’s (TfL) investment programme to create an orbital overground railway network for London.
During Bachy Soletanche’s time on site, the geotechnical specialist has installed approximately 3,650 piles, drilled 74.7km into the ground, used 43,000m2 of concrete and grout, installed 3,050 tonnes of steel and used over 20 different piling rigs to complete the works. The scope included piled foundations for four new stations, five maintenance facility and operational buildings, eight bridges, two viaducts and several other geotechnical structures including embankments across Phase 1 of the project.
Over the course of the project, Bachy Soletanche constructed piles using a variety of techniques including conventional rotary bore large diameter auger (LDA), continuous flight auger (CFA), minipiling (sectional flight auger and conventional types), rotary bore (LDA) under polymer support fluid and rotary bore (LDA) under bentonite, with diameters ranging from 300mm to 2.1m. As well as traditional bearing piles, Bachy Soletanche also installed piles to form contiguous and secant pile walls.
Bachy Soletanche is still on site, completing a variety of mini-piling works at Surrey Quays station using three rigs and installing 125 CFA bearing piles within the Silwood triangle. This is for a pile raft slab using a Simplex SF50, following the acquisition by Bachy Soletanche. The works at Surrey Quays have been particularly challenging due to the tight site access and by working in close proximity to BBCJV’s rail systems teams replacing track for the new railway. The scope comprises the installation of 88 mini-piles constructed either as 14m with 508/450mm diameter fully cased bored and grouted piles, or as 14m deep, 450mm diameter sectional flight auger piles to provide the foundations for pipe crossing slabs to act as protection to sewers intersecting the railway. In addition, a further 80 temporary works minipiles will be constructed to form secant and contiguous walls within the station cutting.
The enormity of the project is no surprise, as the rebranded East London Line will run between Dalston Junction station and New Cross Gate to join the National Rail networks. This will extend the original London Underground line north and south of its existing terminating points and upgrade it to National Rail standards.
Project Engineer for Bachy Soletanche, Martin Stanley commented:
“Looking back, the East London Line project has presented some complicated, but interesting challenges for the dedicated Bachy Soletanche team, both at the design and construction stages. This has included a range of interfaces with existing London Underground Limited (LUL) and National Rail lines that intersect the route at a number of locations, as well as working in close proximity to a variety of stakeholder’s property and assets throughout our works. All in all, we are proud of what we have, and continue to achieve across the project.”
The project is certainly something to be proud of, as Bachy Soletanche was announced as a Highly Commended finalist in the UK Project with a Geotechnical Value over £1 million category at the 2009 Ground Engineering Awards. Bachy Soletanche attended the top industry event, not only as finalists, but also as sponsors of the Young Geotechnical/Geoenvironmental Engineer Award for the second year running.