Professorship for Geotechnics Modèles Physiques en géotechnique
Dr. Jan Laue Ground Improvement
Modelling of Ground Improvement in a Drum Centrifuge
Professorship for Geotechnics Modèles Physiques en géotechnique
Dr. Jan Laue Ground Improvement
Modelling of Ground Improvement in a Drum Centrifuge ETH Drum Centrifuge Inflight Construction of Sand Compaction Piles -
for Ground Improvement under Embankments
Heavy Tamping as Improvement Measure for Double Porous Materials
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
The Drum Centrifuge at ETHZ
View on the safety shield of the ETH Zürich Drum Centrifuge (Springman et al. 2001)
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
The Drum Centrifuge at ETHZ
Channel of the ETH Zürich Drum Centrifuge
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
The Drum Centrifuge at ETHZ • Drum specification Diameter: 2.2 m G max: 440 Drum dimensions: • Depth: 300 mm • Max diameter: 2200 mm • Height: 700 mm
maximum payload: 2000 kg Out of Balance: 10 kgm @ 440 g
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
The Drum Centrifuge at ETHZ
Actuator with CPT tool
Actuator with scraping tool at work
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Test setup using the drum centrifuge with two strong boxes
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Modelling the inflight construction of sand compaction piles in the centrifuge PhD Thesis of Thomas Weber Reference to pictures: Weber, T. 2008: Modellierung der Baugrundverbesserung mit Schottersäulen, IGT Report 232, vdf publisher, ETH Zurich Weber, T.M., Plötze, M., Laue, J., Peschke, G. & Springman, S.M. (2010). Smear zone identification and soil properties around stone columns constructed in-flight in centrifuge model tests, Géotechnique, 60 (3), pp. 197-206
Partners: Swiss National Science Foundation EU Marie Curie Training Network (AMGISS) Federal Office of Transportation Research Fund
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
filling with gravel
insertion
withdrawal
Installation of a sand compaction pile (vibro)
Professorship for Geotechnics Modèles Physiques en géotechnique
Installation of stone columns Preparation of soil models Development of a stone column installation tool Influence of the installation Testing of various grids under embankments
levelling Keller Grundbau
Dr. Jan Laue Ground Improvement
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Model making from clay slurry: in strong boxes (2D) & in drum channel (3D)
construction outside the centrifuge consolidation under the press
construction in the centrifuge consolidation in flight
Professorship for Geotechnics Modèles Physiques en géotechnique
Dr. Jan Laue Ground Improvement
Off topic: How to built a sand model in flight
Densities between D = 25 to 80 % can be reached by air pluviation
Pluviation of sand on a spinning disk
Densities as low as D = -20% can be reached by water pluviation
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Properties of materials
• Clay model: remoulded clay from Birmensdorf
• Stone columns: sieved quartz sand – grain size 0.5 mm < ∅ < 1.0 mm – semi rounded grains, slightly angular – friction angle ϕ': 37°
– classification: CH – clay content: ∅ < 2 µm = 42 % – plasticity: wL = 58 % wp = 19 % IP = 39 % – sensitivity: 1.3 - 2 – friction angle ϕ': 24.5° – cohesion c': 0 kPa
• Embankment: lead balls due to limited height in tub – ∅ = 2.0 mm – density ρ = 6.72 g/cm3
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Centrifuge test on clay model in the strong box preloaded at 100 kPa test at 50 g
T-Bar-testing undrained shear strength su [kPa]
over consolidation ratio OCR [-] 5
10
15
20
25
30
0
0
20
20
40
40
-15 -10
-5
0
5
10
15
20
25
30
35
40
wt_v2
60
depth [mm]
depth [mm]
0
-20
T-bar with load cell F
80 100
wt_v3 wt_v4 calculated
60 80 100 120
120
d
140
L
160
su =
F Nb ⋅ d ⋅ L (Stewart & Randolph 1994)
140 160
su = a ⋅ OCRb ⋅ σ 'v
a = 0.24 b = 0.9
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Centrifuge test on clay model in the drum channel T-Bar-testing
constructed in flight at 60 g test at 50 g
undrained shear strength su [kPa]
over consolidation ratio OCR [-] 0
5
10
15
20
25
-20
30
0
0
20
20
40
40
60
60
-15 -10
-5
0
5
10
15
20
25
30
35
40
wt_v5_e1 wt_v5_e2_3_1 wt_v5_e2_3_2 wt_v5_e4_1 wt_v5_e4_2
depth [mm]
depth [mm]
calculated
80 100
80 100
120
120
140
140
160
160
su = a ⋅ OCRb ⋅ σ 'v
Professorship for Geotechnics
a = 0.24 b = 0.9
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Stone column construction in the drum centrifuge ω pore pressure transducers
axes
flexible sand hose
θ
r
laser scanner
filling tube
lost tip
z r-z-working table
soil model tool table
drum channel
Professorship for Geotechnics Modèles Physiques en géotechnique
Dr. Jan Laue Ground Improvement
Stone column installation tool
Professorship for Geotechnics Modèles Physiques en géotechnique
Dr. Jan Laue Ground Improvement
Model preparation in tub (2D) and drum (3D): placing column grid
COMPARE: Unimproved (L) v. Improved (R)
area ratio of improvement - fs = 10%
area ratio of improvement - fs = 5% & 10 %
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
34 mm
Columns without compaction
Densification
Dry density of column Relative density [%] [g/cm3]
nill
1.50 ± 0.02
48
15 / 10 [mm]
1.77 ± 0.07
165 ???? Clay fills pores in the column
Columns built with additional compaction, e.g. 15mm out – 10mm in
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
ng
rotary coupling
34 mm driving area of working table 30x35 drum channel
α 120
70
35 65 tool table 30 30
10
15
35 70
dimension [cm]
Different lengths of columns occur because of different available lenght of the tube
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Building the embankment
34 mm
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Installation effects: Excess pore water pressure during column construction (2D) compaction excess pore water pressure [kPa]
40
3
PPT 25mm PPT 70mm PPT 120mm
4
30 25 20
1
15 10 5 0 29
penetration depth [mm]
2
35
30
31
insertion 32
33
34
35
36
37
38
39
40
time [min]
GL depth of PPT
0
25 mm
20 40 60
70 mm
80 100 120 29
120 mm 30
31
32
33
34
35
time [min]
36
37
38
39
40
20mm
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Installation effects: heave of clay surface
data points of drum model trend function of drum model container model
3
surface heave [mm]
2.5 2 1.5 1 0.5 0 0
1
2
3
4
5
6
7
8
9
10
11
12
area ratio of ground improvement As / Ag [%]
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Installation effects: on clay structure
6
2 2
[mm] Zone 1 – sand penetrates the clay, mixing of sand and clay - 2 mm thick Zone 2 – high shear strain due to pile installation - max. 2 mm thick Zone 3 – high confining stresses and densification after consolidation - 6 mm Zone 4 – moderate confining stresses and no measurable densification
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Installation effects
Zone 3
Zone 1 Zone 2
ESEM pictures – Environmental Scanning Electron Microscopy 50x 3.5 mm
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
ESEM picture of zone 1 – clay between sand grains
50x
150 µm
800x randomly oriented structure of the clay
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
ESEM picture of zone 2 – clay close to sand grains
50x
150 µm
800x orientation of clay particles due to high shear strain parallel to column axis
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
ESEM picture of zone 3 and 4 – clay far away from sand grains
50x
150 µm
800x randomly oriented structure of the clay
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Results from mercury intrusion porosimetry analysis of clay 4
1.90
36 34
zone 1 2
1.88 3
dry bulk density [g/cm ]
38
porosity [%]
3
32 30
3
4
edge of pile
zone 1 2
edge of pile
40
1.86 1.84 1.82 1.80 1.78 1.76 1.74
28 1.72
26
1.70
0
5
10
15
20
25
30
35
0
5
10
distance to pile axis [mm]
15
20
25
30
35
distance to pile axis [mm]
hyperbolic trend function
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Section of soil model in the tub (2D)
34 mm
12 mm
s H
100 mm
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Pore water pressures after embankment construction (2D) GL
depth of PPT
pore water pressure [kPa]
140
improved not improved
120
1
25 mm
2
70 mm
3
120 mm
100 80 60
3
40
2
20
1 0 0
200
400
600
800
1000
1200
1400
time [min]
acceleration of consolidation by factor 4
10 % reinforcement
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Section of soil model in the drum
100 mm
31 mm
unimproved t90 = 401 min improved t90 = 99 min
12 mm
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Pore water pressures after embankment construction (3D) 110
110
sector 3 – 12%
100
25 mm
90 pore water pressure [kPa]
pore water pressure [kPa]
sector 1 – unimp.
100
90
depth of PPT
80 70 60 50 40 30
80
60 50
30 20
10
10 100
200
300 400 time [min]
500
600
75 mm
40
20
0 0 110
50 mm
70
0 0
700
100
sector 8 – 12%
100
200
300 400 time [min]
500
600
120 mm
700
pore water pressure [kPa]
90 80
Sector 3: t90 = 34 min 2 months (prototype) Sector 8: t90 = 33 min 2 months (prototype)
70 60 50 40
Sector 1: t90 = 330 min 19 months (prototype)
30 20 10 0 0
100
200
300 400 time [min]
500
600
700
acceleration of consolidation by factor 10
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
TimeTime-settlement curves after embankment construction (2D) 0
1
1
①
2
settlement [mm]
2
3
improved
4
not improved
5
②
factor of settlement reduction, n = 1.75
6 7 8 0
② 200
400
600
800
time [min]
10 % area ratio of improvement
1000
1200
embankment height 35 mm lead balls ∆σ = 100 kPa Weber, 2007
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Ground Improvement of double porous material (AMGISS, Marie Curie EU program) -
Fresh landfill. (photograph M. Větrovský)
Reuse of oben cast deposits Centrifuge set Up
-
Use of the drum centrifuge to establish load settlement behaviour in comparison to a field test (PhD thesis Jan Najser, Charles University Prague) and different ground improvement measures (PhD thesis Emma Pooley, ETHZ)
Modelled clay lumps made from real material
Professorship for Geotechnics Modèles Physiques en géotechnique
Stone columns placed in double porosity soils (2D)
Dr. Jan Laue Ground Improvement
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique 56
30.54545455
Distance [mm]
43.27272727
17.81818182
0
13
25 Distance [mm]
38
51
400-480 320-400 5.090909091 240-320 160-240 80-160 0-80
Pressure distribution under the foundation: Test D (7 sand columns)
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Ground Improvement by Heavy Tamping
Axis θ
Drum wall Strongbox
r
Strongbox
17 cm
z
3.7 cm
Guiding tube Model „boulder“ micro concrete (steel)
17 cm
70 cm
Gallery construction
Magnet Actuator Cushion material Gallery
Tool platform
Cushion material Guiding tube Boulder with accelerometer cable
100 cm
Heavy Tamping tool is based on rockfall tool (Chikatamarla et al. 2005)
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Heavy Tamping tool is based on rockfall tool (Chikatamarla et al. 2005) Strongbox
17 cm
Rockfall on a layer of clay lumps
3.7 cm
17 cm
Gallery construction
Cushion material Guiding tube Boulder with accelerometer cable
Adaptions
Professorship for Geotechnics Modèles Physiques en géotechnique
Heavy Tamping tool in use
Dr. Jan Laue Ground Improvement
Professorship for Geotechnics
Dr. Jan Laue Ground Improvement
Modèles Physiques en géotechnique
Erste Ergebnisse
Energy reached in 4 tests (for comparison, 1t falling from 10m heigth equivalent to 100kJ) Net soil pressure vers settlement
Without improvement the foundation reached a net soil pressure of 60kPa at a reference settlement of 15mm
Footprint of foundation: 3.2 model A
3.2 Model B
Professorship for Geotechnics Modèles Physiques en géotechnique
Thank you very much for your attention
Dr. Jan Laue Ground Improvement
