Moorhouse Development – London Deep Sleeved Base-Grouted Piles and Perimeter Retaining Walls

The construction of the deepest base grouted piles in London was a challenge in itself, but to do this in a city center site measuring 85m by 53m in plan and 3.5m below street level was a true achievement. The piled foundations had been designed to isolate the building from future ground movements associated with construction of the CrossRail underground rail tunnels linking east and west London, which would run below the building. To achieve the required isolation, the design of the foundations called for the provision of frictionless pile sleeves to depths of 26m (85ft), and base grouting of the piles - to limit settlement to 20mm (4/5in). 54No. base-grouted piles were installed through London Clay into dense Thanet Sand, to depths of 57m (190ft). This paper describes the construction phase of the work, in particular the processes and methods used to construct the load bearing piles and the removal of obstructions, including coring through existing reinforced concrete piles. Also described is the planning and preparation of the contract and the methods undertaken to overcome the space and environmental constraints