Foundations for the tallest residential building in West London are being undertaken by Central Piling and are on target for completion at the end of next month.
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The £1.25M ground engineering contract on Portal West for main contractor O’Shea Construction involves piling for a basement car park and foundations for four residential towers, including the area’s tallest One West Point.
The A mixed-use development in North Acton it consists of four blocks rising between nine and 42 storeys. The towers will be set around communal courtyard gardens and sit on top of a 6m deep communal basement. When complete, the new development for City and Docklands Property Group will provide 578 new homes as well as new pedestrian routes, public open space, commercial premises and new amenities for the local community.
Central Piling is installing a contiguous piled wall that will facilitate the excavation of the basement, and also the large-diameter bored piles for the deep-piled raft that will support the high-rise buildings.
“The 1050mm diameter bored piles, with depths of 35m, are a first for us and our Soilmec SR-45 and SF-75 rigs are working to their maximum capacity,” said Central Piling managing director Steve Hadley.
“Given the magnitude of the compression loads, we undertook a preliminary pile load test on a 750mm diameter pile loaded to over 10MN which produced satisfactory results. This validated both the design assumptions and the installation technique proposed for the bearing piles.”
Despite the 6m deep excavation which is surrounded by important buildings, including the Consulate of Algeria, the wall design allowed for a cantilever solution for the construction stages, with a minimum amount of locally-installed temporary props and a significant programme saving on the excavation works.
The optimum solution of a temporary cantilever retaining wall formed of 600mm at 750mm centres and large diameter 1050mm and 750mm rotary-bored piles for the piled rafts was the result of a significant amount of pre-construction and design work.
In addition to the current piling work, Central Piling undertook a 44m deep borehole ahead of the foundation work to complement the site investigation works and to obtain more information about the ground conditions.