Geotechnical and Geological Engineering for the Nakheel Tower

Geotechnical and Geological Engineering for the Nakheel Tower

AGS – PERTH – March 2011
Geotechnical and
Geological Engineering
for the
Nakheel Tower, Dubai
Chris Haberfield
1
Outline
1.
2.
3.
4.
5.
6.
7.
8.
9.
Introduction
Ground Investigation
Foundation Concept
Engineering Properties
Test Barrettes
Design Properties
Design Performance
Assessment of Geotechnical Risk
Questions
2
Dubai Trivia
Dubai 1990
„
„
„
Dubai 2003
„
„
„
„
UAE - 7 Emirates
Largest population at 2.3 million
(17 % Emiraties, 42 % Indian, 13 %
Pakastani, 9 % Arabs)
2nd largest in area: 4100 sq kms, 56
km coastline
Import everything but oil (even sand)
Wealth – Oil 5%, trade, real estate
and financial services 95 %
Arabian desert at sea level, 60 %
humidity, 35 – 45oC (summer), 15 –
25oC (winter – 2 months), 80 mm rain
(no stormwater system)
Low seismicity, low tsunami risk
3
Dubai - A Brief History
2006
„
Mangrove swamp 7000 ya, covered in
(calcareous) sand 5000 ya
Earliest documented: 1095 (Dubai),
1799 (Dubai City)
Protectorate of UK in 1892
Constitutional Monarchy - Al Maktoum
family since 1833 – His Highness Sheik
„
„
„
Mohammed bin Rashid Al Maktoum, UAE Prime
Minister and Vice President, Ruler of Dubai (owner
of Nakheel – our client)
The madness. During 2008
Dubai had 15-25% of all the
world’s tower cranes …
4
Dubai Drivers
Ski Dubai
World’s tallest hotel on an
artificial island in the Gulf
Set backs
„ small pox, 1841
„ fire, 1894
„ loss of pearling trade – WW1 and Great
Depression
„ wars with Abu Dhabi (1947 – 1979)
„ Gulf War, 1990 (withdrawal of funds)
„ World economic downturn 2009
Stimulants
„ oil, 1966 (population grew 300 % 1968 75)
„ formation of UAE, 1971; currency (Dirham,
1973)
„ Jebel Ali Free Zone, 1979 (worlds largest
man-made port)
„ 20 year vision (1995)
5
The Dream - The Islands
The World
300 islands
$25-30million each
Palm Jebel Ali
500,000 people
2,000 villas, 40 luxury
hotels, shopping
centres, movie
theatres, and many
other facilities..
From 56 km to 8500 km of coastline
6
The Dream - Dubailand
• 28,000 ha (280 sq km)
• $80 billion
• 45 mega projects, 200 “smaller projects”
7
The Burj Khalifa (formally Burj Dubai)
Worlds tallest building - 826 m
40 % higher than Taipei 101
Opened January 2010
8
March 2008 ~ 630 m
200 m (?) to go
World’s Tallest Towers
Key Structural issues
9
•
Weight (20 GN)
•
Wind
Four Towers in One
Wind Slots
10
Consultant Team
Lead Consultant : WSP
Structural Engineers : WSP, VDM, Les Robertson
Structural Peer Review : Winward Structures
Geotechnical : Golder Associates
Geotechnical Peer Review : Coffey Geosciences
Wind Engineering : RWDI
Wind Engineering Peer Review: U of W Ontario
Architecture : Woods Bagot
MEP : LCI International
Security : Olive Group
Fugro
ME
(site :investigation
contractor)
Fire
/ Life
Safety
Schirmer
Lift
Consultant
Barker Mohandas
LoadTest
(pile: testing)
Quantity Surveyor : Rider Levett Bucknall
Soletanche Bachy – Interfor (piling contractor)
Plus Others
11
Ground Investigation
Site 1
Site 2
12
Site 1
• Extensive ground
investigation at Site 1
• Developed foundation
concept for Site 1
• Ground conditions
similar at Site 2
• Foundation concept for
Site 1 adopted for Site 2
• Ground investigation at
Site 2 used lessons from
Site 1
13
Lessons Learnt at Site 1
„
Founding material (below 20 m depth)
„ “soft” rock, relatively high void ratio (e = 0.6 to 1)
„ massive (no joints) – very young (Quaternary)
„ stress vs strain behaviour dominated by carbonate
and gypsum cementation
Site
2
„ relatively
high stiffness - elastic prior to breaking of
cementitious bonds
(bond
yield strength)
• concentration
on insitu
testing
„ thereafter exhibits high compressibility and creep
• focus
on
„ Best
drilling/sampling
• elastic
stiffness practice - but sample disturbance
significant
• bond yield strength
„ Laboratory
tests affected
by sampleafter
disturbance
• time dependent
displacements
yield
„ Insitu
testing appears to be more reliable
• variability
14
Site 2
180 m
Cored Boreholes
5 boreholes to 200 m
4 boreholes to 150 m
PQ3 triple tube coring
(Borehole to 300 m - Site 1)
„
„
„
„
90 m
Hydrological Boreholes
„
Tower Footprint
6 perimeter boreholes
for water testing
15
Drilling
Moisture contents taken on site
Double vs triple tube coring
All core photographed in splits
Triple Tube Coring
16
Thursday Evening Cricket
17
Australia vs. Pakistan
Core Samples
• selected on site in splits
(immediately after photographing splits)
• immediately plastic wrapped, wax
coated, cardboard tubes
• transported - fragile cargo
• laboratories in Dubai & Australia
(and United Kingdom -Site 1)
18
Golder Field “Hardness” Test
10
BH203
BH205 BH206
BH202 BH201 BH208
BH207BH200
BH204
0
-10
-20
1
6
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
-150
-160
-170
-180
-190
Scratch Hardness Test
• Developed specifically for this site
• Continuous assessment of “hardness” with depth
• Probalistic assessment of variability across the site
19
• Probabilistic
assessment of settlement
• Estimate tilt and differential settlement
Site Hazards
Air conditioner on site
core shed caught fire!
100 mm in 24 hours
Core boxes mostly intact,
core a bit black.
20
Subsurface Stratigraphy
Unit A : Loose,
saturated sands
0m to 6 m
0
Unit B : Variably
Cemented Sands
6 m to 20 m
Depth (m Below Ground Level)
10
20
30
Unit C :Calcareous
Sediments
40
20 m to 77 m
50
(Mostly Calcisiltite)
60
70
80
Unit D : Mudstone with
interbedded Gypsum
90
77 m to >200 m
100
21
Gypsum layers up to
3.5 m thick
Foundation Concept
1.
3. Install
4.
2.
Construct
Install
Make Excavation
Circular
Barrettes
Raft Diaphragm
Slab
Wall
Loose, saturated
sands, 0 m to 6 m
0
Sand
20
Variably Cemented
(variably
Sands
6 m tocemented,
20 m
permeable)
30
Calcareous Sediments
40
20 m to 77 m
50
(Mostly Calcisiltite)
Depth (m Below Ground Level)
10
Rock
60
(higher stiffness
and strength, low
permeability)
Mudstone with
interbedded Gypsum
70
80
90
77 m to >150 m
100
22
Properties of Interest
„
„
„
„
„
Modulus (static, wind,
earthquake)
Bond yield strength
Compressibility
Creep
Shaft resistance
23
Laboratory Testing
„
„
„
„
Non-Specialist (Fugro ME, Dubai)
„ UCS (strength and modulus), Moisture content,
Density, Point load strength index (upper 20 m only),
Chemical testing (carbonate, sulphate, chloride,
magnesium)
Specialist (Monash University, Australia)
„ High pressure oedometer with local strain
measurement (bond yield strength, creep)
„ Constant normal stiffness direct shear testing (shaft
resistance)
Specialist (other – Site 1)
„ Triaxial (strength)
„ Cyclic triaxial (strength and modulus)
„ Resonant column (small strain modulus)
„ Not repeated at Site 2
Strength/deformation test results affected by disturbance
and micro-cracking
24
Conventional Oedometer Testing
0.95
„
„
„
High pressure
Samples affected by
disturbance (microcracking)
Compressibility overestimated
Useful for
understanding bond
strength, consolidation
and creep behaviour
Significant creep
occurred once bond
yield strength exceeded
0.9
0.85
Void ratio
„
Depth = 84.3 m ,including creep
Depth = 84.3 m, excluding creep
Depth = 90.65 m, including creep
Depth = 90.65 m, excluding creep
Depth = 108.8 m, including creep
Depth = 108.8 m, excluding creep
0.8
0.75
0.7
0.65
0.6
100
1000
Effective Pressure (kPa)
25
10000
Oedometer Testing
(Local Displacement Measurement)
„
Time (min)
Local displacement
measurement
Impact on creep
rate
1
10
100
1000
10000
0
0.02
Local displacement measurement
Platen displacement measurement
0.04
0.06
Settlement (mm)
„
0.08
0.1
0.12
0.14
900 kPa to 1820
0.16
0.18
26
100000
Resonant Column, Cyclic Triaxial Tests
„
„
„
Strain dependency of modulus
Compliance affects (testing) unresolved
Consistent (but lower) with insitu testing (pressuremeter,crosshole seismic)
100
Young's Modulus (GPa)
BH8, 36.7 m
Bh12, 79.1 m
BH7, 114.8 m
10
BH7, 133 m
BH7, 182.5 m
1
0.1
0.001
0.01
0.1
1
Strain (%)
27
CNS Direct Shear Tests
Shaft resistance
purely frictional
800
Depth = 31.95 m
Depth = 39.75
700
Depth= 46.35 m
Depth = 51.9 m
600
Depth = 63.65 m
Shear stress (kPa)
Depth = 84.10 m
37 deg
500
39 deg
400
300
200
100
φ = 37o
0
0
100
200
300
400
500
600
Normal stress (kPa)
28
700
800
900
Insitu Testing
„
„
„
„
Shallow SPT testing
„
sand density
Pressuremeter testing
„
3 boreholes
„
Testing at 5m intervals up to 200 m
„
Measurement of insitu Young’s
modulus, strength and creep
properties
Water pressure testing
„
6 boreholes
„
200 m
„
Measurement of in-situ permeability
Cross hole and down hole seismic testing
„
2 locations (6 boreholes)
„
200 m
„
Continuous measurement of insitu
small strain modulus
29
Pressuremeter Tests
R.L. (m) DMD
Sample
disturbance and
stress relief
(impact on initial
modulus)
Initial loading Modulus Ei (MPa)
1000
10000
Pressuremeter Shear Strength (MPa)
100000
0
0
0
-20
-20
-40
-40
-60
-60
-80
-80
-100
-120
-140
-160
BH204 Pressuremeter
BH203 Pressuremeter
BH208 Pressuremeter
UCS E
R.L. (m) DMD
Laboratory
UCS tests
underestimate
insitu strength
and stiffness
100
2
-100
-120
-140
-160
-180
-180
-200
-200
30
1
BH204 Pressuremeter
BH203 Pressuremeter
BH208 Pressuremeter
UCS/2
3
4
5
6
Pressuremeter Tests
„
„
Similarity between Ei and
Eur consistent with
dominance of cementation
and massive structure
Creep (hold tests) also
undertaken
Unload/reload Young's modulus, Eur (MPa)
100000
BH204
BH203
BH208
10000
Ei = Eur
1000
100
100
1000
10000
Initial loading Young's Modulus Ei (MPa)
31
100000
Cross hole Seismic Tests
Initial Modulus Ei (MPa)
100
1000
0
Cross hole seismic
(reduced by factor of 5) for
comparison with
pressuremeter tests
-20
-40
-60
-80
E pressuremeter
R.L. (m) DMD
„
Ecrosshole
≈
5
-100
-120
-140
BH204 - Pressuremeter
BH203 - Pressuremeter
-160
BH208 - Pressuremeter
BH202 3m Seismic
BH201 6m Seismic
-180
-200
32
10000
Test Barrettes
Three trial barrettes 2.8 m x 1.2 m, 2 x
65 m deep, 1 x 95 m deep
„
Osterberg Cell Testing
„
Rated 54 MN (5,400 tonnes)
„
Achieved 80 MN (8000 tonnes)
„
Two levels of O-Cells
„
Confirm Performance
„
Shaft and base resistance
„
Cycle shaft
„
Long Term Base (creep)
„
Deformation properties
„
Construction aspects
„ meters
Base drilling – cleanliness
Soil strain
„
Cross-hole sonic testing
„
Constructability
„
33
Hydrofraise & Polymer Plant
34
Osterberg Cells & Reinforcement
35
Base Drilling
36
Testing (My home for 26 days)
37
Loading Sequence – TB03
90
Stage 1
Stage 2
Stage 3
Stage 4
81 MN
80
Lower O-Cell
70
Upper O-Cell
70 MN
O-Cell Load (MN)
60
50
Hold
periods
40
Cyclic loading
of shaft
30
20
10
0
22/03 0:00
22/03 12:00
23/03 0:00
23/03 12:00
24/03 0:00
Date and Time
38
24/03 12:00
25/03 0:00
25/03 12:00
Test Results - UOC
90
Upper O-Cell Top Plate
TB01
Upper O-Cell Bottom Plate
80
Upper O-Cell
70
Upper O-Cell Load (MN)
62 m to head
of barrette
Upper plate
60
50
40
Lower plate
30
20
10
12.4 m shaft
+ base
0
-4
39
-2
0
Displacement (mm)
2
4
Measured Base Responses - LOC
90
TB02 Soil strain meter (0.6 m below barrette toe
TB02 Barrette toe tell-tale
80
Base
debris
TB03 Barrette toe tell-tale
70
60
LOC load (MN)
Soil strain
meters
TB03 Soil strain meter (1.1 m below barrette toe)
50
40
30
20
10
0
0
20
40
60
80
Displacement (mm)
40
100
120
140
Base Resistance
60
10
9
50
Barrette base bearing pressure (MPa)
8
Soil strain meters
Ebase = 1.0 to 1.2 GPa
LOC Load (MN)
40
30
20
TB01 (Soil strain meter)
10
7
6
5
4
3
2
TB02 (Soil strain meter)
TB03 (Soil strain meter)
1
0
0
0
10
20
30
Barrette toe displacement (mm)
41
40
0
10
20
30
Displacement of Barrette Toe (mm)
40
Base Creep
Time (mins)
1
10
100
0.0
Settlement (mm)
0.5
1.0
1.5
2.0
TB02,
TB03,
TB01,
TB01,
TB03,
TB02,
TB03,
TB02,
TB03,
Estimated increase in vertical
Estimated increase in vertical
Estimated increase in vertical
Estimated increase in vertical
Estimated increase in vertical
Estimated increase in vertical
Estimated increase in vertical
Estimated increase in vertical
Estimated increase in vertical
stress
stress
stress
stress
stress
stress
stress
stress
stress
=
=
=
=
=
=
=
=
=
1.2 MPa
1.7 MPa
1.9 MPa
3.0 MPa
3.1 MPa
3.4 MPa
3.5 MPa
4.0 MPa
4.5 MPa
2.5
42
Soil strain meters
1000
Shaft Resistance – Cyclic Loading
1500
Average shaft resistance (kPa)
1000
Average shaft resistance (kPa)
800
600
400
200
Mobilised shaft resistance :
500
Shaft displacement (mm)
0
-20
-200
0
20
40
60
80
100
120
• 550 kPa to 600 kPa at RL -55 m
0
-400
TB02
• >1250 kPa 1at RL-85 m (gypsum)
-600
-4
-800
-500
No degradation
pre-peak under one way and two way loading
Average shaft resistance (kPa)
800
No degradation
post-peak
under
one
way cyclic loading (wind/earthquake)
-1000
600
Degradation (net tension)
post-peak under two way cyclic loading (not a design case)
TB01
-1500
Shaft displacement (mm)
TB03
400
200
Shaft displacement (mm)
0
-20
-200
0
20
-400
-600
-800
43
40
60
80
100
120
Summary of Test Barrette Performance
Mobilised Shaft Resistances and Base Bearing Pressures
Test Barrette
TB01
TB02
TB03
Maximum mobilised shaft resistance
between UOC and LOC
1250 kPa
550 kPa
600 kPa
Maximum mobilised base bearing
pressure
13.6 MPa
11.6 MPa
16.8 MPa
Maximum Test Barrette Loads Mobilised during Testing
Test Barrette
TB01
TB02
TB03
Maximum load mobilised at UOC
81 MN
48 MN
69.5 MN
Maximum load mobilised at LOC
75 MN
60.3 MN
81.4 MN
Maximum load mobilised on
shaft between UOC and LOC
81 MN
35.2 MN
38.4 MN
Equivalent total load mobilised
during testing
(design structural ultimate load)
237 MN
143.5 MN
189.3 MN
(96 MN)
(96 MN)
(96 (MN)
44
Estimated Head of Barrette Performance
400
350
Test Barrette
TB01
TB02/
TB03
Ultimate shaft capacity
370 MN
168 MN
Ultimate base capacity
85 MN
72 MN
Ultimate capacity
(geotechnical strength)
455 MN
240 MN
Design ultimate
structural load
96 MN
96 MN
Barrette head load (MN)
300
250
200
TB01
150
TB02 and
TB03
100
50
0
0
50
100
150
1 MN = 100 tonnes
Barrette head displacement (mm)
45
Design Geotechnical Model
NW
SE
NE
SW
Gypsum
layers
N
NW
SW
NE
SE
46
Design Properties
“Bond Yield” Strength
Modulus/strength ratio
Pressuremeter
0
100
200
Ei/2su
300
400
500
600
0
-20
-40
Adopt su = Ei/600
R.L. (m) DMD
-60
-80
-100
-120
-140
-160
-180
BH204 - Pressuremeter
-200
BH203 - Pressuremeter
BH208 - Pressuremeter
47
Design Properties
Strength and Stiffness
Pressuremeter Shear Strength (MPa)
0
100000
0
0
-20
-20
-40
-40
-60
-60
-80
-80
R.L. (m) DMD
R.L. (m) DMD
100
Initial loading Modulus Ei (MPa)
1000
10000
-100
-120
-140
-160
BH204 Pressuremeter
BH203 Pressuremeter
-120
-160
Design Line
-180
-180
-200
-200
48
2
-100
-140
BH208 Pressuremeter
1
BH204 Pressuremeter
BH203 Pressuremeter
BH208 Pressuremeter
Design Line
3
4
5
6
Design Properties
Variation
Correlation
between field
hardness and
modulus
Probabilistic
analysis
10
BH203
0
-10
-20
-30
-40
-50
BH205 BH206
BH202 BH201 BH208
BH207BH200
BH204
Pressuremeter modulus (MPa)
6000
5000
Mean + 1 Standard Deviation
4000
Mean
3000
2000
1000
Mean - 1 Standard Deviation
-60
-70
-80
-90
0
0
1
2
-100
-120
-140
-150
-160
4
Hardness
-110
-130
3
49
5
6
7
Design Properties
Creep Rate
Creep rate
¾ Oedometer
¾ Test barrettes
Increased creep
rate above bond
yield stress
3.5
Creep rate (% per log cycle of time)
¾ Pressuremeter
4
Pressuremeter
Test Barrettes
3
Oedometer
2.5
⎛ ( p − po ) ⎞
Creep rate = 0.5⎜⎜
− 1⎟⎟
su
⎠
⎝
2
1.5
1
0.5
Keep stress increase -1
below bond yield strength
0
0
1
2
3
4
Normalised increase in stress in
excess of initial insitu stress
50
5
( p − po )
su
6
Design Properties
Shaft Resistance
Shaft resistance, τ
Shaft friction (kPa)
0
500
1000
0
CNS direct shear tests
Test Barrette TB01
Test Barrette TB02
purely frictional
φ= 37o (CNS direct shear)
Test Barrette TB03
-20
Theoretical
Theoretical x 0.85
τ= σntanφ
τ = 8 z (lower)
τ = 9.1 z (best)
τ =12.5z (upper)
.
..
.
.. . .. .
.
-40
. . . ..
...
.
.
.. .
.
.
.
.. .
Normal
stress
RL (m DMD)
Buoyant weight of
fluid concrete, σn
-60
-80
Shaft
friction
.
.
.
.
.
. . .. .
.
-100
. . . ..
...
-120
51
1500
Design Performance
Test Barrettes
100
80
Measured vs
Predicted
performance
60
70
Load at LOC (MN)
Prediction
based on design
property profiles
80
Load at UOC (MN)
Class A
prediction
90
70
50
40
30
Theoretical - clean base
60
50
40
30
TB02 - based on soil strain meter
20
Theoretical : clean base
TB02 - based on soil strain meter
TB03 - based on soil strain meter
20
10
10
0
0
0
10
20
30
Displacement at UOC (mm)
40
0
50
100
52
200
Displacement at LOC (mm)
(b) LOC
(a) UOC
150
250
Design Performance
Vertical Key Structural Elements
“Hammer” Mega-Column
Mega-Columns
Hammer Wall
Barrettes located
under main structural
columns and walls
Inner Drum Wall
Fin Wall
53
Design Performance
Footing Layout
Barrette toe levels
• -55 m DMD
• -60 m DMD
• -79 m DMD
Barrette sizes
• 1.5 m x 2.8 m
• 1.2m x 2.8 m
Raft thickness
• 2.5 m
• 4.0 m
• 6.0 m to 8.0 m
54
Design Performance
Base Debris
„
Construction
„ observed in test barrettes
„ cause identified
„ changes to installation process
„
Design
„ little difference to design settlements (2D)
„ design for full base resistance and no base resistance
(worst case base debris)
„ potential higher stresses near barrette toes
„ use gypsum layer (drum wall) and stagger barrette
lengths (hammer walls) to distribute loads in shaft
resistance
55
Design Performance
2D PLAXIS
0
Distance from centre line between Hammer Walls (m)
5
10
15
0
• base stresses
• base debris
• staggered length barrettes
• target gypsum layers
• barrette toe depths
Increase in vertical stress (MPa)
-1
-2
-3
-4
-5
0 m below barrette toe
1 m below barrette toe
2.5 m below barrette toe
7.5 m below barrette toe
-6
-7
-8
-9
(b) With base debris
56
20
Design Performance
3D PLAXIS
50
Design Property
Cases
40
30
• Best guess
20
10
• Lowest credible
0
• Highest credible
-10
Design Load Cases
-20
Working load
-30
-40
• DL + LL
-50
• DL + 0.8 WL
-50
-40
-30
-20
-10
0
10
20
30
40
50
-50
-40
-30
-20
-10
0
10
20
30
40
50
50
• DL + 0.75 LL + 0.6 WL
40
Ultimate load
30
• 1.2 DL + 0.5 LL + WL
20
• 1.2 DL + 0.5LL + E
+ base shear
10
0
-10
Design base
conditions
• Full base resistance
-20
-30
-40
• No base resistance
-50
57
Design to work under all design cases and combinations
Design performance
Stresses Beneath Barrettes
Ultimate
wind load
case
Working
wind load
case
-55.5 m DMD
-60.5 m DMD
-79.5 m DMD
MPa
58
Design Performance
Settlement
Global Settlement
DL + LL
With and without
base debris
Radius from Centre of Tower (m)
0
10
20
30
40
50
0
-10
Tilt (WL) = +/-10 mm
Best estimate
80 mm to 85 mm
Differentials
20 mm
Occurs during
construction
Settlement (mm)
-20
-30
-40
clean base
-50
-60
-70
-80
-90
-100
base debris
59
60
Design Performance
Tilt and Settlement Range
1
Probabilistic
analysis
0.9
Hardness vs E
profiles
BH201
BH202
BH203
BH204
BH205
BH206
BH207
BH208
0.8
0.7
0.6
Probability
95 % probability
< 150 mm
3D analysis using
credible upper
bound properties
0.5
0.4
0.3
0.2
3D analysis using
credible lower
bound properties
0.1
0
0
50
100
150
200
250
Settlement (mm)
Analyses indicate tilt under gravity loads not significant
60
Design Performance - Barrette Actions
Bending Moments
and Shear Force
Shear Force (kN)
-4000
-2000
0
2000
Bending Moment (kNm)
4000 -4000
-2000
0
0
0
2
2
4
4
6
6
8
8
10
10
12
12
Design ultimate WL
Shear forces dissipate
6 m from head of
barrette
Bending moments
dissipate 16 m from
head of barrette
Depth below raft (m)
Finite Element
analysis
Depth below raft (m)
Group effects
14
16
18
20
14
16
18
20
61
2000
4000
6000
Design Performance - Equivalent Stiffness
Equivalent Stiffness
Ring
Radius (m)
For structural analysis
Spring
Stiffness
MN/mm
Better model of ground
1
49.0
0.56
Iterative process
2
46.5
0.50
3
44.0
0.52
4
41.0
0.51
5
39.0
0.58
6
36.0
0.78
7
33.5
0.56
Refine footing system
Pile Groups
Mega Column 3 x 3 pile group
Raft Stiffness (kPa/mm)
12
10
Inner Drum 4 x 3 pile group
8
8
31.0
0.61
9
28.0
0.65
10
25.5
0.52
11
23.0
0.43
20.5
50
0.29
60
18.0
0.29
6
4
2
0
0
10
20
30
12
40
Radius from centre of tower (m)
13
62
Values derived for
Raft and barrettes
DL + LL (long term)
WL (short term)
Assessment of Geotechnical Risk
Risk Mitigation
• comprehensive
„
„
ground investigation
(best practice)
„
„
• comprehensive
insitu & laboratory
testing
„
„
• advanced analysis
• prudent design
• proving
performance
Investigation and Design Measures
„
Geotechnical Risk Register
„
Identifies and assesses geotechnical hazards
„
„
• monitoring
• contingencies
Potential geotechnical issues
Design objectives to manage issues
Geotechnical investigation to investigate issues and design
control measures
Design of control measures
Expected outcomes
„
related to inadequacy of control measures
unidentified ground issues
Contingency plan and mitigation
63
Construction began early 2008
D-wall guide walls
D-Wall complete
About 200 barrettes have been completed
Site : April 2008
Excavation of first
D-wall panel
64
EFF’s
Golder Associates
Darren Paul
Max Ervin
(and many others)
Thank you – Questions ?
65