As part of the redevelopment of New Union Wharf, an existing 1970s East Thames residential estate located on the Isle of Dogs, Central Piling were appointed by Hill Partnerships to supply a piling solution for new residential development to be carried out in several phases. The proposed Continuous Flight Auger (CFA) piling system proved ideal in implementing initiatives towards the high water table and minimalising disruption to the existing community as much as possible.

Ground Conditions

The ground conditions comprised 8.5m of made ground and alluvium, underlain by 3.5m of sand and gravel River Terrace Deposits. Very stiff clays of the Lambeth Group were identified between 12m- 22.5m, underlain by up to 2m of Lambeth Group sand and gravel. Dense sands from the Thanet Sand Formation were encountered from depth 24.5mbgl. Groundwater was encountered at approximately 2.4mbgl.

Challenges and Solution

Piles were designed according to BS 8004 and during phase 1, the factor of safety employed was 3 negating the need for working test piles. For phase 1, Continuous Flight Auger (CFA) piles of diameters 400mm and 450mm with a length range between 9m and 27.3m were proposed to achieve maximum horizontal loads of 150kN and compressive loads of up to 1550kN. It was justified that to achieve the higher bearing capacities, bearing piles would have to be founded in the sand layer of the Thanet Sand Formation however this proved problematic to penetrate with a conventional 40T CFA rig.

Central Piling’s flexible and logistical approach to install the CFA piles amidst the extremely dense ground conditions using a 55T CFA rig equipped with a double- skinned tungsten carbide rock auger, ensured penetration into the bedrock and that the required design depth and load capacities were achieved by the bearing piles.

Further to the successful completion of the piling works required for Phase 1, subsequent phases for the New Union Wharf redevelopment have since being awarded to Central Piling by Hill Partnership who look forward to completing the regeneration by 2021.