THE SCHEME
Property developer, Greenland Group, appointed Bachy Soletanche as the Principal Contractor on their flagship scheme by Canary Wharf. Spire London will be Western Europe’s tallest residential tower; soaring 67 storeys above the listed buildings of West India Quay’s historic waterside, the building will offer unrivalled views across the city.
Bachy Soletanche’s contract included the demolition of an existing basement and slab, the enabling works, along with the design and installation of the geotechnical package, including the piling, capping beam and partial bulk dig for the Spire London.
DEMOLITION AND ENABLING
Bachy Soletanche appointed specialist demolition contractor, Cantillon, to dismantle and remove the existing basement and ground floor slab from the original building, Hertsmere House. Once complete, the team could commence the enabling works to ensure the piling operations could proceed safely and on programme. As part of the enabling works a large bentonite farm was installed on the site to provide the team with enough support fluid to undertake the extensive drilling required.
CONSTRUCTION
The geotechnical element was split into two areas, a retaining wall to form the basement, and rotary bored bearing piles to support to superstructure. Prior to the piling operations commencing, the team installed two test piles to validate the proposed design. Using the maintained load static pile testing method, the two piles managed to reach loads of 108MN and 103MN, breaking the UK record in the process. The working load on the piles will only reach 40MN but due to an applied factor of safety of two, the piles needed to be tested to at least double this.
Following the successful test, the team began installing the retaining wall and the bearing piles. The secant piled wall is 220 linear metres, bored to a depth of 15m with a retaining height of approximately 7m. The piles were installed using a BG46 piling rig in CSP mode to ensure verticality. The team also constructed 66 bearing piles, between 1800mm and 2100mm in diameter, bored to a depth of up to 67m.
Two Crossrail tunnels run beneath the site and due to their location, particularly one running through the centre of the site, a protective 4m thick reinforced concrete raft, bridging the tunnel will be installed. The raft will be supported by the bearing piles either side of the tunnel to ensure the loading does have not have any adverse effects on the tunnel.
PRINCIPAL CONTRACTOR
Bachy Soletanche’s ability to operate as the Principal Contractor allowed the client to proceed with development of the site, at the same time as procuring the main contractor for follow-on build.
Responsibilities during this phase included; overall site management and security, health and safety of all personnel on site, client liaison and community engagement. This experience was invaluable to the client and ensured that the site was handed over to the follow-on trades for the main structural build to commence.
