Bachy Soletanche piling at Crossharbour site

Bachy Soletanche Limited has recently completed its first stage of piling works at Crossharbour, the high-profile development based in London City centre.

Leading geotechnical specialist, Bachy Soletanche Limited has recently completed its first stage of piling works at Crossharbour, the high-profile development based in London City centre - constructing a secant wall around the perimeter of the substantial 6.8 acre site.

The former London arena site is based in the heart of the Canary Wharf and Docklands business district and is one of the largest ongoing construction sites in London City centre.

The prestigious waterfront location is planned to provide a myriad of facilities comprising 1047 residential apartments, 285,846 sq ft of offices, a four star hotel and a combined 40,846 sq ft of retail, restaurants and leisure facilities.

Barry Osborn, contracts manager at Bachy Soletanche Limited, commented: "Currently the site leaves a redundant space on the Millwall Inside Dock, however construction works are well underway as Bachy Soletanche has recently completed the secant wall piling works".

"We were awarded the initial piling work for the secant wall in October last year and within four months the approximately 577lm long wall is now complete and ready for excavation" He added.

The initial secant wall contract comprises of approximately 970 secant piles, and due to the ground profile and the client requirement of a strict 1:200 tolerance two processes are being utilised to construct the wall.

Barry Osborn explains: "The use of two different processes is required for the construction of the female and male piles as the design requires complete accuracy".

"This is mainly due to the waterfront location of the site ensuring that the wall is completely watertight before excavation".

The female piles were drilled to a depth of 14metres and constructed prior to the male piles using a bespoke piling method designed by Bachy Soletanche.

Barry Osborn commented: "Once the female piles were installed the 485 male piles were ready to construct".

"These used a longer length casing at 17metres, had a stronger concrete mix and a different installation method to the female piles".

The 750mm diameter male piles, with a 14metre depth were drilled using 17metre casings with the same length auger string.

These piles were drilled utilising a cased continuous flight auger method (CSP), which was the preferred method due to the structure of the ground which at 14metres had a clay layer - forming a natural seal for the toe of the wall.

With the secant walls complete, Bachy Soletanche will remain on site as the geotechnical firm was awarded the main works contract for the bearing piles and the capping of the secant wall.

Barry Osborn concluded: "The original on-site time scale at Crossharbour was four months but then we were awarded the main works contract, extending the programme by another two months".

"This caused a cross over for both the secant wall contract and the bearing piles contract, which resulted in the need for careful co-ordination to ensure the project ran smoothly".

"However, now the secant wall is complete we can concentrate on the bearing piles which are due to be completed in April".

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