Recent Innovations to Facilitate the Construction of Large Diameter Piles in London-Paper

Paper

Pdf Summary

The paper describes construction innovations used for large-diameter rotary piles at Battersea station on London’s Northern Line Extension. The project required deep piles, up to 2.4 m in diameter and approximately 60 m long, built alongside diaphragm-wall works in challenging ground conditions.<br /><br />Polymer support fluid was adopted for the piles as an alternative to bentonite. This reduced pressure on the site’s bentonite storage and treatment facilities and supported concurrent construction activities. A full-scale trial pile confirmed that polymer could support excavation over an extended period and helped establish site procedures for mixing, testing and quality control. Because local mains water hardness reduced polymer performance, the water was pre-treated with sodium hydroxide to raise its pH to 10.5. The trial also identified suitable methods for monitoring polymer properties.<br /><br />The project used distributed fibre-optic temperature sensing (DTS) to assess pile integrity and observe concrete placement. Sensors attached to the reinforcement cage recorded temperature continuously along the pile, capturing the rising concrete head during tremie concreting and the heat released during cement hydration. This provided a detailed temperature profile rather than measurements at isolated points, and enabled an early integrity assessment within 48 hours.<br /><br />Results showed that temperature development varied with depth and ground conditions, and that most hydration heat was generated during the first 24 hours. The measurements also demonstrated the potential of DTS to reveal concrete-flow behaviour and support pile-quality assessment.<br /><br />Overall, the trial validated polymer-supported construction and distributed temperature sensing for large piles, offering practical benefits for construction logistics, quality control and understanding of pile performance.

Keywords

Battersea station

Northern Line Extension

large-diameter rotary piles

polymer support fluid

bentonite replacement

deep foundation

diaphragm wall

distributed fibre-optic temperature sensing

pile integrity

tremie concreting