Large-diameter piles in chalk - part 2, design and construction

摘要

The design of a 60-storey tall residential tower with a two-level basement in east London has had to take account of two London Underground tunnels which pass beneath the centre of the site, resulting in 'working' pile loads of up to 45 MN. The foundation solution comprised a stiff raft with cast in situ bearing piles up to 2.4 m dia. and 61 m long founding in the grade A/B chalk stratum. Some piles, using bentonite support fluid, needed to be constructed within the tunnel exclusion zones, which required a concession from London Underground. This paper presents the Osterberg-cell preliminary pile load test and results, foundation design, working pile construction and limitations on piles constructed in the London Underground exclusion zones. The paper also discusses the control on the bentonite support fluid properties and monitoring of its properties during pile construction.