s - WTCB

Transcription

s - WTCB

Sense and sensitivity of
pile load-deformation behaviour.
Ir. Flor De Cock
Geotechnical Expert Office GEO.BE
Goals of my lecture

To sensitize and to encourage you (and others) to consider
more often the deformability of piled foundations
To contribute to the understanding of the load-deformation
behaviour of piles
To demonstrate the relevance and importance of
considering the SLS both for individual piles as for pile
groups
To demonstrate the use of transfer functions – in particular
of the hyperbolic type – as a practical tool to interpret as
well as to predict the pile deformation behaviour.
What about Eurocode 7 –
Geotechnical design ?

December 2004 : EN 1997-1:2004 was
unanimously ratified by European Member States
To be accompanied by “National Annexes” as
link between the EC7-1 and national standards
Around 2009 (?), after 2-year calibration period,
EC7-1 becomes valid and relevant national
standards have to be withdrawn
EC7-1 and pile design

A lot of attention to ULS design
SLS design of piles only briefly considered, e.g. :

“7.6.4.1(1) Vertical displacements under serviceability limit state conditions
shall be assessed and checked against the requirements given in 2.4.8 and 2.4.9”
“7.6.4.2 (for compression piles) NOTE When the pile toe is placed in a mediumdense or firm layer overlying rock or very hard soil, the partial safety factors for
ultimate limit state conditions are normally sufficient to satisfy serviceability limit
state conditions.”
“7.6.4.2 (2) Assessment of settlements shall include both the settlement of
individual piles and the settlement due to group action.”
“7.6.4.2 (4) When no load results are available for an analysis of the interaction of
the piles foundation with the superstructure, the load-settlement performance of
individual piles should be assessed on empirically established safe
assumptions.”
“7.6.4.3 (for tension piles) NOTE Particular attention should be paid to the
elongation of the pile material.”
Content of the paper

Data-bases of well documented pile load tests on bored
and auger piles, available in Belgium
(Briefly) Description of the calculation methods considered in some
National design standards (NL-F-G) to assess the load-deformation
curve of single piles
The use of hyperbolic transfer functions (HTF) as a
powerful tool for analysis, back-calculation, prediction and
sensitivity-analysis of the load-settlement curve of single
piles of different types and in different soil conditions.
Some illustrations where the deformation behaviour of
piles merits to be considered and/or has strongly influenced
the design or the behaviour of the structure
Database 1
(F. De Cock, 2001)
27 screw piles
Period 1970-2000
Pile type
Shaft bearing Shaft+end
bearing
End bearing
Atlas
0.5 - 0.75 %
0.75 – 1.50 %
1.5 – 1.75 %
Fundex
No data
0.75 – 1.0 %
0.75 – 1.25 %
Omega
0.5 – 0.75 %
No data
2.0 – 2.5 % *
Note : normalised versus
Qu=Qasymptotic
Database 2
20 piles in sand (Limelette a.o.)
16 piles in clay (SKW a.o.)
Period 2003-2007
(BBRI)
Clay - Screw piles
100
Q/Q_s0=10%Db,eq (%)
Sand - Screw piles
120
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
80
60
40
20
100
Q/Q_s0=10%Db,eq (%)
120
S12
S13
S14
S15
S16
S17
S18
S19
S20
80
Qu=Qconv 10%
60
40
20
0
0
0
2
4
6
8
s0/Db,eq (%)
10
12
14
0
2
4
6
8
s0/Db,eq (%)
Pile type
Shaft bearing
Shaft+end
bearing
End bearing
Screw piles
0.5 – 1.0 %
No data
0.75 – 1.5 %
10
12
14
Database 2
20 piles in sand (Limelette a.o.)
16 piles in clay (SKW a.o.)
Period 2003-2007
(BBRI)
Clay - All piles
Sand - All piles
120
100
Q/Q_s0=10%Db,eq (%)
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
80
60
40
20
0
100
Q/Q_s0=10%Db,eq (%)
120
S1
S2
S3
S4
S12
S13
S14
S15
S16
S17
S18
S19
S20
S26
S27
S28
S29
S30
S31
S32
80
60
40
20
0
0
2
4
6
8
s0/Db,eq (%)
Pile type
10
12
14
0
2
Shaft bearing
0.5 – 1.0 %
Bored and CFA
0.5 % bentonite
1.0 – 1.5%
casing
6
8
s0/Db,eq (%)
End bearing
Driven Precast concrete 0.5 – 0.75 %
Screw piles
4
1.0 – 2.0 %
No data
0.75 – 1.5 %
0.5 – 1.5 % *
10
12
14
Calculation methods of pile loadsettlement in National Codes

NL : NEN 6743 : semi-graphical method based on
normalised mobilisation charts for base and shaft resistance :
DISPLACEMENT & BORED PILES
G : DIN 4014 : 4 tables with values of experience of
mobilisation of base and shaft resistance : BORED PILES
F : Fascicule 62-V : analytical method based on bilinear
elasto-plastic mobilisation curves : NO REGARD TO PILE
TYPE
See also Van Impe (BAP 1-1988) for screwed piles
Request to the audience : other (National) methods available ?
Hyperbolic transfer functions
Atlas screw pile
b=
Qmob ( kN )
0
202
403
603
805
1003
1204
1403
1602
1803
2003
2201
2303
2357
st ( mm )
0.00
0.68
1.16
1.42
2.00
2.57
3.29
4.47
5.91
7.87
11.09
16.97
22.47
29.65
st/Qmob
0.0000
0.0034
0.0029
0.0024
0.0025
0.0026
0.0027
0.0032
0.0037
0.0044
0.0055
0.0077
0.0098
0.0126
s/Db
(%)
0
0.25
0.5
1
2
2.5
3
4
5
6
7
8
9
10
15
30
s Chin
(mm)
0.00
1.63
3.25
6.50
13.00
16.25
19.50
26.00
32.50
39.00
45.50
52.00
58.50
65.00
97.50
195.00
Qmob
(kN)
0
789
1220
1678
2066
2167
2239
2337
2399
2443
2475
2500
2520
2536
2584
2635
0.001455
Diam. 51/65
Estimated Qu-inf=
Qu at s=10%Db
2688 kN
2536 kN
0.014
y = 0.000372x + 0.001455
0.012
(/)
Q = s/(as+b)
a=
0.000372
s 10% =
65 mm
s / Qt

Extended use of curve fitting to
extrapolate the measured loadsettlement curve
Basis equation Q=s/(a+bs)
transformed in s/Q=a+bs
Pile N° P16
Chin Analysis
0.010
0.008
0.006
0.004
0.002
0.000
0
Pile head displacement (mm)

Koekelare 1992
0
0
10
20
30
40
50
10
20
30
Pile Head displacement (mm)
500
1000
1500
2000
40
Load (kN)
2500
3000
mathematical backgrounds

See Fleming (1972), Caputo (BAP 4-2003)
Separate hyperbolic equations for base and shaft resistance
sb
Base : Rb =
with K = 3.(1 −ν 2 ). f ≈ 0.54 withν = 0.4 and f
Kb +

Shaft :
sb
ss
Rs =
s
Ks +
b
Rbu
or
Rsu
ss
qs =
s
Ks + s
4.Db .Eb
with (Fleming,1972)
q su
Parameters :

Db .Eb
Eb = secant modulus at 25% of the ultimate stress
Ms = shaft flexibility factor (nature of angular rotation)
Ks =
= 0.85
M s .Ds
Rsu
Particularities of the hyperbolic functions :

Kb and Ks correspond to the tangent slope at the origin
0.212.Db .qbu or thus s
b50% proportional to pile base Ε
s50% = K b .Rbu =
Eb

s 50% = K s .R su = M s .D s
0.00
or thus ss50% proportional to pile shaft Ε
0.50
Rb/Rbu
1.00
Kb
Displacement

Parameters :

Eb = secant modulus at 25% of the ultimate stress
Ms = shaft flexibility factor (nature of angular rotation)
Eb in non-cohesive soils :

(Caputo, 2003) : Eb ≈ 10 qc
My estimations :
Eb = 4 to 6 x qc for bored piles in NC-sands
Eb = 6 to 8 x qc for bored piles in OC-sands
Eb = 8 to 12 x qc for screw piles
Eb = 15 to 20 x qc for driven piles

Eb in stiff OC-clays : Eb = 50 to 80 qc or Eb ≈ 750 to 1.000 x cu

Ms ≈ 0.001 – 0.002 (Fleming, 1992) (Caputo, 2003)
A multipurpose tool

Discretising the pile, e.g. in 20 elements
Define (by calculation or curve fitting) :

Transfer functions for base :
Transfer functions for shaft :
Rb =
sb
s
Kb + b
q s ,i =
Rbu
s s ,i
s
K s ,i + s ,i
q su ,i
A panoply of applications
1.
2.
3.
4.
5.
(class A)-prediction of the LS curve
Back-analysis of SPLT
SLS-design of single pile
Conversion of SPLT to other pile geometry
Inversion of SPLT

From compression to tension
From bi-directional to top loaded PLT
6. Evaluation of impact of e.g. pile type, material,
shape, execution method, … on SLS
7. Evaluation of influence of boundary
conditions, e.g. downdrag, excavation of top
layer, …
Prediction, back-analysis and design

All 3 applications in relation to the behavior of screw
piles in stiff OC-clay
Extended research program 2000-2001, with SPLT on
2 prefab concrete piles and 10 screw piles (Fundex, De
Waal, Olivier, Omega & Atlas)
Prediction event : prediction of
ultimate resistance and static
load-settlement behaviour :
q c (MPa), q b u
D epth (m)

0
0
10
(m )
20
30

By calculation on the basis of
soil tests
By deduction from dynamic pile
load tests
from E B 2
Qst from MB 23
10
Qst from MB 12
15
40
Σ fs/1,35
5

(MP a), Q s t /2,5 (kN )
50

Basic “Belgian” design methodology based on CPT
(Holeyman et al., 1997 – ERTC3 Seminar)

Base resistance :
Rbu = α b .ε b .qbu . Ab
( m)

or = α b,mean .ε b .qbu ,mean . Ab
Shaft resistance :
R su = X s ∑ H i .η pi .q ci = X s ∑ H i .α si .η *pi .q ci

Role playing parameters : αb, αs, Eb and Ms (or Kb
and Ks), EA-pile
Hyperbolic transfer functions (HTF)

Application 1 : prediction of LS-curve by calculation
from CPT and using HTF (De Cock, 2001 – Istanbul)
Application 2 : back-analysis and curve fitting of Qt, Qs
and Qb to deduce “individually” the required HTF
parameters to calibrate a chosen design method (in this
case a semi-empirical direct design based on CPT, as
published in the Belgian EC7-NA)
Application 3 : calculate the LS-curve, using the
prescribed pile installation factors
Example of prediction – assumptions
Ultimate base :
Rbu = α b,mean .ε b .qbu ,mean . Ab
Ultimate shaft :
Rsu = X s ∑ H i .α si .η *pi .qci
Base flexibility :
0 .54
Kb ≈
Db .E b

Shaft flexibility :
M s . Ds
Ks =
Rsu

Ec : concrete modulus : 30,000 MPa

Example of prediction – Olivier screw pile
St-Kat-Waver Olivier 36/51-7.4 m
α b,mean=0,81 α s=1,25
0
200
400
600
Qb, Qs, Qt (kN)
800
0
10
sh (mm)
20
30
40
50
60
70
αb,mean = 0.81
αs = 1.25
Eb = 70 qc ≈175 MPa
Ms = 0.0015 for z<5 m
0.0010 for z>5 m
Ec = 30,000 MPa
1000
1200
Example of back-analysis – assumptions
Ultimate base :
( m)
Rbu = α b .ε b .qbu
. Ab
Ultimate shaft :
Base flexibility :
0 .54
Kb ≈
Db .E b

Shaft flexibility :
Ks =

Ec : concrete modulus : ?

M s . Ds
Rsu
De Beer-Van Impe
η *pi = 1 / 30 × qc
Example of back-calculation – Olivier screw pile
St-Kat-Waver Olivier 36/51-7.4 m
α b,mean=0,81 α s=1,25
0
200
400
600
Qb, Qs, Qt (kN)
800
1000
St-Kat.-Waver Olivier B4 36/51-7.4 m
α b=0,95 - α s=1.25
1200
0
0
0
10
10
20
20
200
400
600
800
Qb, Qs, Qt (kN)
1000
1200
0
40
Class A-prediction
30
40
1
5.0%
2
3
Back-calculation
4
10.0%
50
50
5
60
60
6
70
70
7
αb,mean = 0.81
αs = 1.25
Eb = 70 qc ≈175 MPa
Ms = 0.0015 for z<5 m
0.0010 for z>5 m
Ec = 30,000 MPa
αb = 0.95
αs = 1.25
Eb = 65 qc ≈160 MPa
Ms = 0.0045
Ec = 25,000 MPa
s-el (mm)
30
sh (mm)
sh (mm)
2.5%
Example of design – based on NAD-EC7
Ultimate base :
( m)
Rbu = α b .ε b .qbu
. Ab
α b = 0.8
Ultimate shaft :
α s = 0.9
Base flexibility :
0 .54
Kb ≈
Db .E b

Shaft flexibility :
Ks =

Ec : concrete modulus : ?

M s . Ds
Rsu
η *pi = 1 / 30 × qc
As from back-analysis
Ec = 25,000 MPa
Example of design – Olivier screw pile
α b=0,95 - α s=1.25
0
200
400
600
800
Qb, Qs, Qt (kN)
1000
NA-factors α b=0,8- α s=0.9
0
1200
400
600
800
1000
1200
0
0
0
200
Qb, Qs, Qt (kN)
2.5%
2
3
30
Back-calculation
sh (mm)
5.0%
s-el (mm)
20
sh (mm)
10
1
10
20
30
4
40
50
5
50
60
6
60
70
7
70
40
10.0%
SLS design calculation
αb = 0.95
αs = 1.25
Eb = 65 qc ≈160 MPa
Ms = 0.0045
αb = 0.80
αs = 0.90
Eb = 65 qc ≈160 MPa
Ms = 0.0045
Ec = 25,000 MPa
Ec = 25,000 MPa
Prediction/back-analysis/design – Fundex screw
St-Kat-Waver Fundex A3 38/45 - 11,5 m
α b,mean=1,0 - αs=0,8
Qb, Qs, Qt (kN)
200
400
600
800
1000
1200
0
1400
200
400
600
800
1000
1200
0
St-Kat.-Waver Fundex A3 38/45 - 11.5 m Qb, Qs, Qt (kN)
NA-factors α b=0,8- α s=0.9
0
1400
0
0
0
1
10
30
40
50
60
Class A-prediction
40
10.0%4
40
50
5
50
6
60
7
70
Back-calculation
αb,mean = 1.00
αs = 0.8
Eb = 70 qc ≈175 MPa
Ms = 0.0015 for z<5 m
0.0010 for z>5 m
Ec = 30,000 MPa
400
600
800
1000
1200
1400
30
3
60
200
20
30
70
70
2
sh (mm)
5.0%
20
20
s-el (mm)
2.5%
10
10
sh (mm)
sh (mm)
0
St-Kat.-Waver Fundex A3 38/45 - 11.5 m Qb, Qs, Qt (kN)
α b=0,85 - α s=0,96
SLS design calculation
αb = 0.85
αs = 0.96
Eb = 50 qc ≈125 MPa
Ms = 0.002
αb = 0.80
αs = 0.90
Eb = 50 qc ≈160 MPa
Ms = 0.002
Ec = 35,000 MPa
Ec = 25,000 MPa
Use of hyperbolic transfer functions to analyse
compression and tension behavior on CSG-piles

CSG-piles : Continuous Shaft Grouted piles
Installed by screwing in of steel tube (e.g. Ε140 mm),
provided at the base with screw blades or with an
enlarged drill bit
During screwing-in :
injection of cement-grout
which is mixed with the
surrounding soil
qc (MPa) and FR (% )
0
10
+0.0
-5.0
Test pile TP1 diameter 140/450
-10.0
Level (m)
Load-testing program –
Pijnacker 2006
-15.0
-20.0
-25.0
-30.0
-35.0
-40.0
Test pile RP2 diameter 140/180
20
30
Load-testing program –
Pijnacker 2006
Initially : analytical interpretation of
test results hindered by :
Uncertainty on axial pile stiffness EA
Large share of s-elastic in total pile head
displacements
Mal-functioning of tell-tales
Accuracy of tell-tale measurements to
be questioned
Analysis by curve-fitting
with hyperbolic transfer
functions, maybe ?
Curve-fitting of pile TP1 in compression
Micropaal
Pijnacker
TP1-druk
Diam. 140/450
Verification of installation factors
CPT
Cone type
Soil type base
Soil type shaft
Fugro TP1 Site level
E Water level
-1.5 NAP Diameter drill tool
Nom. Diam. base
sand Nom. Diam. shaft
sand Pile length
Ult. shaft resistance defined at pile element displacement of :
0.45m Fabr. Date
0.45m Test date
0.45m Concrete
24.50m Reinforcement
1.0 x Ds Ult. base resistance defined at base displ.
Shaft resistance
From Zi
Hi
Fs-CPT
ΔFs-CPT
(m)
(m)
(kN)
(κΝ)
(kN/m²)
0
1.5
10000
1.5
13.0
11.5
4.0
600
6000
17.0
24.5
7.5
14000
Calculated
1000
2000
αs
(−)
0.018
0.018
0.018
0.018
CPT
(kN)
(-)
(kN/m²)
191
TP1
12000
88
305
Eb
0
0
10
10
30
40
50
60
(kN)
1.00
0.90
1.26E+06
EA
buis+2meetbuizen+grout inwendig
waaruit
1/Kb
105000
Rbu
1718
Pile head load (kN)
3000
20.4
mm
(−)
αp
(−)
1336
1920
0
20
140000kPa
1.0 x Db
Rekstijfheid
Base resistance
εb
pru
Rsu
0
qc-average
6/12/2005
grout
tube 139.7x10
20
1000
Total
3638
2000
Pile head load (kN)
3000
2.2 mm
18.2
mm
30
40
50
60
70
70
80
80
Total resistance-calculated
Base resistance
Shaft resistance
Measured
s-el calculated
sb-calculated
s-el measured
sb measured
Converting compression test into tension test
Pile head load (kN)
Pynacker-CSG-pile TP1

αb = 0.0
αs = same as in
compression
EA only on steel
section (not on grout)
-80
-70
-60
-50

-40
-30
-20
-10 0
500
1000
1500
2000
2500
0
10
20
30
40
50
60
Calculated by curve-fitting
of compression test:
αb = 0.9; αs = 0.018
70
80
Base resistance
Shaft resistance
Measured
3000
Pile head load (kN)

αb = 0.0
αs = same as in
compression
EA only on steel
-80
Conversion of
compression curve :
αb = 0.0; αs = 0.018
-70
-60
-50

-40
-30
-20
-10 0
500
1000
1500
2000
2500
0
10
20
30
40
50
60
αb = 0.9; αs = 0.018
70
80
Base resistance
Shaft resistance
Measured
3000
Pile head load (kN)

αb = 0.0
αs = same as in
compression
EA only on steel
-80
Conversion of
compression curve :
αb = 0.0; αs = 0.018
-70
-60
-50

-40
-30
-20
-10 0
500
1000
1500
2000
2500
0
10
20
30
40
50
60
αb = 0.9; αs = 0.018
70
80
Base resistance
Shaft resistance
Measured
3000
Curve fitting for tension pile
Micropaal
Pijnacker
RP2-trek
Diam. 140/180
Verification of installation factors
CPT
Cone type
Soil type base
Soil type shaft
-1.5 NAP Diameter drill tool
Nom. Diam. base
sand Nom. Diam. shaft
sand Pile length
Fugro RP2 Site level
E Water level
Ult. shaft resistance defined at pile element displacement of :
0.18m
0.18m
0.18m
26.50m
Fs-CPT
(kN)
500
ΔFs-CPT
(kN)
1000
qc-average
(kN/m²)
12000
500
6000
15000
Calculated
αs
(−)
0.0230
0.0300
0.0230
0.0230
Rsu
(kN)
156
106
351
1658
2272
Pile head load (kN)
1500
2000
0
0
10
10
20
30
40
50
60
70
“7.6.4.3 (for tension
piles) NOTE Particular
attention should be paid
to the elongation of the
pile material.”
55
1.0 x Db
Rekstijfheid
Base resistance
εb
pru
CPT
(-)
RP2
αp
EA
(kN)
(−)
(−)
1.000
1.00
9.91E+05
EA van : buis + 2 meetbuizen
(kN/m²)
1
0
0
0
Hi
(m)
1.0
12.5
4.5
8.5
15/12/2005
grout
tube 139.7x10
1.0 x Ds Ult. base resistance defined at base displ.
Shaft resistance
From Zi
(m)
0
1.0
13.5
18.0
26.5
Fabr. Date
Test date
Concrete
Reinforcement
500
1000
Pile head load (kN)
1500
2000
12
20
30
40
43
50
60
70
80
80
Shaft resistance
Measured
Total
2272
s-el calculated
s-el measured
sb-calculated
sb measured
A panoply of applications
1.
2.
3.
4.
5.
(class A)-prediction of the LS curve
Back-analysis of PLT
SLS-design of single pile
Conversion of PLT to other pile geometry
Inversion of PLT

6.
7.
From compression to tension
From bi-directional to top loaded PLT
Evaluation of impact of e.g. pile type,
material, shape, execution method, … on SLS
Evaluation of influence of boundary
conditions, e.g. downdrag, excavation of top
layer, …
See case histories
Case Histories to illustrate sense and
sensitivity of pile displacements
Importance of pile displacements in the design
1.
2.
3.
ULS of the pile foundation: what is the real load on the
different piles ?
ULS of the structure: which stresses are developing in the
superstructure due to the displacements of the piles ?
SLS of the structure: are the settlements (or heave) of the piles
and the pile groups admissible for the structure and its
functioning ?
Is related to pile-structure interaction :
•Stiffness of the superstructur
•Stiffness of the piles (individually or in group
Demonstration of sensitivity of interaction
Beam 40 m – 6 column loads 1.000 kN
Assumption 1 : ∞ stiff beam; ∞ stiff piles
Pile load (kN)
Superstructure with infinite stiffness
1600
1400
1200
1000
800
600
400
200
0
1375
1375
1150
700
700
350
10
8
350
6
4
2
0
Pile stiffness infinite
-2
-4
-6
-8
Distance (m )
-10
Assumption 2 : ∞ stiff beam; piles as springs
Pile load (kN)
1600
1400
1200
1000
800
600
400
200
0
1375
1375
1150
700
700
350
10
8
350
6
4
2
0
-2
Piles with equal spring stiffness
-4
-6
-8
Distance (m )
-10
Assumption 3 : ∞ stiff beam; piles with different spring
stiffness (group effect for concentration in the center)
Pile load (kN)
1600
1400
1200
1000
800
600
400
200
0
1333
1375
1333
1375
1150
667
350
10
8
6
4
700
667
667
2
0
700
667
667
-2
Piles with different spring stiffness
-4
350
-6
-8
Distance (m )
-10
Assumption 4 : flexible beam; ∞ stiff piles
Pile load (kN)
Superstructure with finite stiffness
1600
1400
1200
1000
800
600
400
200
0
1375
1375
1150
700
700
350
10
8
350
6
4
2
0
-2
-4
-6
-8
Distance (m )
-10
Assumption 5 : flexible beam; piles as springs
Pile load (kN)
1600
1400
1200
1000
800
600
400
200
0
11931375
11931375
944
9481150
944
700
389
700
389
350
10
8
350
6
4
2
0
-2
-4
-6
-8
Distance (m )
-10
Assumption 6 : flexible beam; piles with different spring
stiffness (group effect for concentration in the center)
Pile load (kN)
1600
1400
1200
1000
800
600
400
200
0
1193
1193
1375
1375
944
9481150
949700
952
944
1182
389
1182
949700
389
350
392
10
8
350
392
6
4
2
0
-2
Piles with different spring stiffness
-4
-6
-8
Distance (m )
-10
Case History 1 : New residential
development – former ship yard Temse

Structural Engineers : Buro Mouton/Ghent
Piling : De Waal Palen
Vibrex driven piles 1.500 kN
Ε508 mm – Length 13 m
Load : =/- 100,000 kN
Central core : 47,300 kN
Case History 2 – Antwerp Left Bank
Built in 1978, on pile foundation
New owner 2007
Nearby the “Galgenweel” (gallows pool,
swirl” originating from dike bursting
Case History 2 – Antwerp Left Bank
Various cracking in subbase and superstructure
Tilting of 97 mm to the direction of the pool
qc (MPa)
0
10
20
30
40
50
10
i = 97/15000 = 1/154
Level (m)
5
0
-5
-10
-15
CPT1
-20
CPT2
CPT3
60
70
80
Case history 3 – high-rise/NL
Joustra et al – 9th ICSMFE,Tokio. 1977
Well documented case history.
But : do we learn from our lessons ?
Case history 4 – houses Jette/Brussels
1
2
3
Case history 4 – houses Jette/Brussels
Case history 4 – houses
Jette/Brussels
House No. 1 : built in the 60’s
21 driven Franki piles, 500 kN
Length +/- 13.5-14.0m >< ground level
In period 1990-1995 : small fissuring at
the interface 1-2
Estimated settlements : 3 mm left, 8-9
mm right
No.2
qc (MPa)
0
10
20
30
40
50
+0.0
+5.0
Depth (m)
House No. 2 : built in the 1989
Includes a subbase
15 Atlas screw piles 36/46 cm, 350 kN
Length +/- 10.0 m >< ground level
No.1
+10.0
+15.0
+20.0
+25.0
Total CPT-friction Fs (kN)
Jette/Brussels
House No. 3 : built in 1995
17 piers (blind pits) 1.2 m, 240 kN
Length +/- 6.9 m >< ground level
No.2
No.3
qc (MPa)
0
10
20
30
40
50
+0.0
+5.0
Depth (m)
Serious damage and tilting of house
No. 2 in 1st week after excavation and
concreting of the piers.
Increased damage during and after
erection of house No. 3
No.1
+10.0
+15.0
Tilting of 1/20 of common wall 2/3
Estimated settlement : 5 mm left, 35
mm right
+20.0
+25.0
Total CPT-friction Fs (kN)
Jette/Brussels
Influence of load on the piers :
settlements underneath the pier base
Consequently :
(4)Loss of Rs+ from 6.9 to 10 m, even
inversion to Rs(5)Settlements underneath pile base
0
No.2
10
No.3
20
30
+0.0
3
+5.0
Depth (m)
Influence of pier installation : soil
decompression (stress reduction)
and/or subsidence of the soil.
Consequently :
(1)Loss of Rs+ up to 6.9 m
(2)Even inversion to Rs- up to 6.9 m
(3)Rs- on the subbase wall
No.1
1
2
4
+10.0
5
+15.0
+20.0
4
Jette/Brussels
No.1
No.2
No.3
Pile head load (kN)
0
100
200
300
400
500
600
700
0
(1) Loss of positive skin
friction up to 6.9 m
2
10
20
30
+0.0
3
(2) Negative skin friction
on pile shaft up to 6.9 m
6
(3) Negative skin friction
on subbase wall
8
10
12
+5.0
Depth (m)
4
0
1
2
4
+10.0
5
14
(4) Loss of positive skin
friction from 6.9 to 10.0 m
16
+15.0
18
20
Total pile resistance
Base resistance
Skin friction
+20.0
4
Case history 5 – MAS/Antwerp
Museum aan de Stroom – under construction
Client :
: Stad Antwerpen
Architect
: Neutelings-Riedijk
Consulting eng. : ABT België nv
Proj.-Management : Bureau Bouwtechniek
Contractor
: Ass. Interbuild-Willemen-Cordeel
Scheldt
Bo
na
pa
W
il l
em
rte
do
k
do
k

Square footprint 40x40m²
10 floor levels 6 m high
Museum floors containing a gallery
and a museum floor
Stacked in such a way that the MAS
becomes a spiral tower
Periphery – with 6-m high outside
glass façades – conceived as a
walking boulevard
The architectural conception
resulted in a type of Christmas
tree structure

Central Core 12x12 m²
(>< footprint of 40x40 m²)
Absence of load bearing façades
Large projection of the periphery
with framework or concrete wallbeams
In realtime : www.mas.be
Case history – MAS/Antwerp
The foundation aspects
qc (MPa)
+10.0
+5.0
+0.0
Level (m)
Permanent load : +/- 200,000 kN
Variabel load : +/- 95,000 kN
On central core : 85% or 250,000 kN
0
-5.0
-10.0
-15.0
-20.0
-25.0
-30.0
10
20
30
40
0
+10.0
+5.0
Level (m)
CFA piles
Ε900 and 600 mm
Service load 3000 kN and 2000 kN
+0.0
-5.0
-10.0
-15.0
-20.0
-25.0
Post-grouted bored piles
Ε1070 and 900 mm
-30.0
Service load 7500 kN and 3900 kN
10
20
30
qc (MPa)
40

Shorter piles
Smaller single pile displacement
Smaller group settlement in deep
clay
Experience available
(Maertens et.al, 2003 – BAP IV)
Bored pile 1.28 m/post-grouted
α b=0.6, ξ f=1.5
Head load (kN)
0
2000
4000
6000
8000 10000 12000 14000 16000 18000
0
20
s/D = 2.5%
Head displacement (mm)
Post-grouted bored piles :
40
60
s/D = 5%
80
100
120
s/D = 10%
140
Base resistance
Grouting 10-16.5 m
Grouting 5-16.5 m
No grouting
CPT after grouting
Expected settlement behavior
+10.0
+5.0
Level (m)
0
+0.0
-5.0

Individual pile settlements :
estimated from HTF
Group settlements : based on the
equivalent raft approach
-10.0
-15.0
-20.0
-25.0
-30.0
10
20
30
qc (MPa)
40
Expected settlement behaviour
0
+10.0
Level (m)
+5.0
+0.0
-5.0
Total load (kN)
0
50000
100000
150000
Group settlement (mm)
0
200000
9
10
250000
9
300000
350000
-10.0
10
-15.0
20
24
29
30
40
50
60
Settlement in sand
total settlement center core
total settlement façades
42
39
-20.0
59
-25.0
49
70
-30.0
10
20
30
qc (MPa)
40
Measures against differential settlement behaviour

Use of flat jacks ? Not accepted by the client.
Structural measurements :
No continuous stiff concrete walls going from
central core to façade
Floor slabs between central core and façades are
isostatic (hinge supports)
Compressive concrete on the floor elements delayed

Monitoring of settlements asked for

So what about the settlement measurements ?

Only useful data from the centre core
Only rough estimation of total load in different
stages
Total load (kN)
0
50000
100000
150000
200000
250000
300000
0
Group settlement (mm)

10
20
24
29
30
40
Settlement in sand
50
total settlement center core
60
Measured
70
39
42
49
59
350000
Conclusions

My hope :

That this lecture has contributed to encourage and improve your
sensitivity (and sensibility) for pile deformation behaviour
My acknowledgements :
Ir. Monika De Vos & Noël Huybrechts (BBRI)
Ir. Ben Notenboom (ABT) & Bart De Ridder (Buro Mouton)
Flemish government and the IWT (Institute for the Promotion of
Innovation by Science and Technology in Flanders)

My thanks