Terminal 5, Heathrow Airport
Description of Work
GCG is part of the design team, working alongside TPS, Mott Macdonald and Laing, working on the new
terminal proposed for Heathrow by British Airports Authority. GCG is advising on geotechnical issues
related to:
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Site investigation
earthworks, including soil stabilisation and temporary cut slope stability
design of piles in swelling ground
predictions of ground and tunnel movements
A key role has been the design, supervision and interpretation of a ground investigation aimed at making
the best estimate of the in situ stiffness, strength and expansibility of the London Clay. The ground
investigation included rotary cored samples, thin wall tube samples, cross-hole geophysics, detailed
logging, advanced laboratory testing, self-boring pressuremeter and permeameter testing.
GCG is also assisting with the general design of the earthworks and with checking of the design of
temporary and permanent slopes and earth structures. GCG is heavily involved in both the design and
monitoring of temporary slopes; a particular concern is the possible presence of deep-seated tectonic
shear surfaces. Finite element analyses of the slopes have been carried out and the slopes are being
monitored using inclinometers, tensiometers and surveying techniques.
A large-scale field earthworks trial has been conducted including the measurement of surface wave
velocities in order to characterise the condition of the London Clay fill. The results of the field trial, together
with other testing on site have been used to assess movements of the aircraft pavement and services and
to develop strategies for conditioning the clay fill in order to reduce the risk of out-of-tolerance movements.
A programme of pile load testing was proposed with the aim of examining changes in pile capacity with
time and allowing predictions of the effects of heave movements on pile behaviour.
GCG have assessed the impact of overall changes in
the site level on longitudinal movements of new bored
tunnels for the Piccadilly Line and Heathrow Express
under the site.
GCG assisted Imperial College in the preparation of a
successful proposal for funding from the Engineering
and Physical Sciences Research Council for a
detailed laboratory investigation of the London Clay at
Heathrow Terminal 5. Work is now proceeding with
the collection of high quality block samples and
advanced laboratory testing including hollow cylinder
tests on intact samples
Client: British Airports Authority
Dates: 1998 to present
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