The document discusses the design and construction of the foundations for the new Wembley Stadium in London. Extensive pile foundations were installed, with pile lengths up to 40m, to support the large stadium structure. Key aspects discussed include the non-linear finite element analysis of pile groups using Repute to model the lifting of the large 133m triumphal arch. Precise monitoring of pile group movements during the lift showed good agreement with the non-linear predictions, highlighting the importance of accounting for soil non-linearity.

1. Case study – Wembley Stadium
Dr Andrew Bond, Geocentrix Ltd
Dr Francesco Basile, Geomarc Ltd

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Experience from new Wembley Stadium
• With 90,000 seats, the new
Wembley stadium will be the
largest football stadium in the
world with every seat under
cover. There will be NO
obstructed views.
• The main architectural feature is
a 133m high triumphal arch,
7.4m in diameter, with a weight
of 1,750 tonnes. With a span of
315m, it is one of the largest
and most slender structures in
the world.
• Construction of 4000 piles, pile
diameter 0.45-1.5m, pile lengths
up to 40m. Extensive pile
testing programme.

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Experience from new Wembley Stadium
• Design by Mott MacDonald who
performed extensive Repute
analyses (both linear and non-
linear) of pile groups during raising
of triumphal arch.
• Large pile groups subject to
complex loading (V, H, M, T)
– soil non-linearity essential
for realistic prediction
• During raising of the arch,
monitoring was installed to
determine the movements of the
pile groups. These were compared
to Class A predictions from Repute
(see Hardy & O’Brien, 2006, for
more information).

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Ground conditions
• Made ground (varying thickness)
• 30-35m London Clay
– unit weight γ = 20 kN/m3
– undrained strength
• Cu = 40 + 7.5z kPa (z in m) for z < 10m
• Cu = 115 + 4.5z kPa (z in m) for z ≥ 10m
– Young’s modulus stiffness anisotropy:
• Vertical Ev = 60-232 MPa (depending on strain level)
• Horizontal Eh = 9-171 MPa (ditto)
• Chalk
• Water table at 2.5m depth

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Shear modulus from seismic cone self-boring
pressuremeter
0
5
10
15
20
25
30
35
40
0 100 200 300 400
Shear Modulus at Small Strain (MN/m2
)
Depth
below
Top
of
London
Clay
(m)
SBP
SCPT
Weathered
London Clay
Unweathered
London Clay
Unit A
Lambeth Group
Unit B

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Using linear model to match lateral pile tests
• Ev drops: 232 MPa (initial) 118 (FoS = 1.7) 60 (failure)
• Eh drops: 171 MPa (initial) 23 (FoS = 1.7) 9 (failure)
• Non-linear analysis essential if large lateral loads exist
0
100
200
300
400
500
0 20 40 60 80
Lateral Movement (mm)
Horizontal
Load
(kN)
Back analysis using
linear elastic model
Over-
conservative
design
Unconservative
design

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Using non-linear model to match lateral pile
tests
0
100
200
300
400
500
0 20 40 60 80
Lateral Movement (mm)
Horizontal
Load
(kN)
Test Data
Single pile testing
Non-linear
0
100
200
300
400
500
0 20 40 60 80
Lateral Movement (mm)
Horizontal
Load
(kN)
Test Data
Single pile testing
Non-linear

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Arch lifting mechanism
Arch
Stillage
Base
Arch at
Original
Position
Turning
Struts
Jacking
Points
Original Position
of Arch
Western
Arch Base
Jacking
Bases
Turning Struts
Eastern
Arch Base
• The most critical engineering activity during the stadium
construction was raising the arch to its final position (112o)

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Design of permanent Eastern Arch Base
• Pile group
– No. 19 Piles (L =33m, D =1.5m)
– Spacing: Sx = SY = 5m
• No. 121 load cases covering each angle of the arch at
5o intervals
• “Observational method” applied:
– System of precision levelling (+/- 0.1mm) to determine
movements of pile groups (settlements, deflections, rotations)
during the arch lift
– On the basis of the non-linear Repute analyses, amber and
red limits were set

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Comparison Repute vs measured behaviour:
pile-group deflection in y direction
-4
-2
0
2
4
6
8
10
12
14
0 20 40 60 80 100 120
Angle of arch: degrees
Deflection
in
y
direction:
mm
Measured
Repute
Amber limit
Red limit

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Conclusions (from Hardy O’Brien, 2006)
• “The predicted movements correlated very well with
the observed movements and illustrate the
importance of non-linear soil behaviour in modelling
pile groups.
• If linear analyses had been undertaken, the
movements and structural forces could have been
under or over estimated by a considerable amount.
• Consequently the amber and red limits would have
been set incorrectly and the safety of the arch lift
could have been compromised”.