Canary Wharf and Heron Quays, London
Description of Work
GCG was appointed Category III geotechnical checker by Tower Hamlets Building Control for the Canary Wharf
Phase II and Heron Quays developments. The construction of the Jubilee Line Extension has resulted in a surge in
construction activity in the Docklands area of East London, currently Europe’s largest commercial development,
comprising 25 individual sites, and including the construction of two 40 storey towers and several deep basements.
The buildings are supported by large diameter bored piles, up to 1.5m diameter, 33m long and founded in the dense
Thanet Sand Formation. Base grouting was conducted on all of the piles in order to minimise pile settlements at
working load and maximise the contribution from the pile base.
The geotechnical designer, Arup Geotechnics, sought to improve the foundation design through the development of
new pile design methods and the employment of piled raft foundations in the Heron Quays area. Four instrumented
pile load tests were conducted, two in tension and two in compression, with strain gauges and extensometers to
identify the base load and shaft resistance through the different strata. Dewatering of the lower aquifer was
conducted to enable the piles to be bored dry. However, the resulting increase in effective stress meant enhanced
capacities for the test piles in the short-term. Recharge wells were installed around two of the piles in an attempt to
simulate the long-term pore pressure conditions, including the effects of rising groundwater. New effective stress pile
design methods were developed so that the effects of dewatering could be taken into account. Typical pile testing
loads reach 30MN. Plate load tests were performed to measure the stiffness of the Lambeth Clay for raft design.
GCG conducted a thorough review of Arup Geotechnics’ pile test interpretation and proposed design methods for
single piles and piled rafts. A parametric study of the foundation settlements was conducted, examining the possible
variations due to changes in ground stiffness. The piled wall designs were checked and the effects of construction
on adjacent structures were also examined. During construction, GCG was at hand to discuss and review changes
to the methods of construction and pile testing procedures and examine the possible causes behind unexpected load
test results. After construction, the effects of defects and remedial measures were reviewed in the close-out reports.
Client: London Borough of Tower Hamlets Building
Control
Dates: 1999 to present
Estimated piling costs: £20 million
View of Canary Wharf Phase II and Heron Quays areas
GEOTECHNICAL CONSULTING GROUP
1A Queensberry Place, London, SW7 2DL, United Kingdom
Tel: +44(0)20-7581-8348 Fax: +44(0)20-7584-0157 email:admin@gcg.co.uk