Piling solutions from Central Piling help to save time on excavation works on a new prestigious residential development in West London.

Central Piling is providing piling solutions on a massive basement car park and foundations for four residential towers at a prestigious new development which will include One West Point, which will be the tallest residential building in West London.

The Portal West development is being built by O’Shea Construction. 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 the 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 company was brought in as the piling specialist sub-contractor by O’Shea Construction. This enabled Central Piling to be involved in the project from an early stage, providing advice and support in choosing the piling solutions.

Central Piling began work on the £1.25 million geotechnical contract in November, with construction of the embedded basement retaining wall, which is formed of 600mm diameter continuous flight auger (CFA) piles. The installation of the rotary-bored bearing piles began soon after, with the entire contract scheduled to be complete by the end of February (2019).

The tallest of the four towers, One West Point, is a 42-level tower situated in the prime position of the centre of the North Acton/Old Oak Regeneration area. When complete, the building will be the tallest residential landmark in West London, with the highest private sky garden and terrace bar in the whole of the capital.

Steve Hadley, managing director of Central Piling, said: “High-rise buildings such as this require large-scale foundation systems capable of transferring the loads to suitable ground. 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.

“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.”

Central Piling, who offer a full range of geotechnical services as well as pile design and construction, also undertook an additional 44m deep borehole to complement the site investigation works and to obtain more information about the ground conditions.

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.