Modelling of Ground Improvement in a Drum Centrifuge Modelling of

Professorship for Geotechnics

Ground Improvement

Dr. Jan Laue

Modèles Physiques en géotechnique

Modelling of Ground Improvement in a Drum

Centrifuge


Ground Improvement

Dr. Jan Laue


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


Ground Improvement

Dr. Jan Laue


The Drum Centrifuge at ETHZ

View on the safety shield of the

ETH Zürich Drum Centrifuge

(Springman et al. 2001)


Ground Improvement

Dr. Jan Laue



Channel of the

ETH Zürich Drum Centrifuge


Ground Improvement

Dr. Jan Laue



• 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


Ground Improvement

Dr. Jan Laue


Actuator with CPT tool Actuator with scraping tool at work



Ground Improvement

Dr. Jan Laue


Test setup using the drum centrifuge with two strong boxes


Ground Improvement

Dr. Jan Laue


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


Ground Improvement

Dr. Jan Laue


Keller Grundbau

filling with gravel insertion withdrawal levelling

Installation of a sand compaction pile (vibro)


Ground Improvement

Dr. Jan Laue


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


Ground Improvement

Dr. Jan Laue


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


Ground Improvement

Dr. Jan Laue


Off topic: How to built a sand model in flight

Pluviation of sand on a

spinning disk

Densities between D = 25 to 80

% can be reached by air

pluviation

Densities as low as D = -20%

can be reached by water

pluviation


Ground Improvement

Dr. Jan Laue


Properties of materialsProperties of materialsProperties of materialsProperties of materials

• Clay model:

remoulded clay from

Birmensdorf

– 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

• Stone columns:

sieved quartz sand

– grain size 0.5 mm < ∅ < 1.0

mm

– semi rounded grains,

slightly angular

– friction angle ϕ': 37°

• Embankment:

lead balls due to limited

height in tub

– ∅ = 2.0 mm

– density ρ = 6.72 g/cm3


Ground Improvement

Dr. Jan Laue


0

20

40

60

80

100

120

140

160

0 5 10 15 20 25 30

over consolidation ratio OCR [-]

depth [mm]

Centrifuge test on clay model in the strong boxCentrifuge test on clay model in the strong boxCentrifuge test on clay model in the strong boxCentrifuge test on clay model in the strong box

0

20

40

60

80

100

120

140

160

-20 -15 -10 -5 0 5 10 15 20 25 30 35 40

undrained shear strength su [kPa]

depth [mm]

wt_v2

wt_v3

wt_v4

calculated

preloaded at 100 kPa �� test at 50 g

= ⋅ ⋅ σb

u vs a OCR 'a = 0.24

b = 0.9

T-Bar-testing

u

b

Fs

N d L=

⋅ ⋅

T-bar with load cell

F

d

L

(Stewart & Randolph 1994)


Ground Improvement

Dr. Jan Laue


Centrifuge test on clay model in the drum channelCentrifuge test on clay model in the drum channelCentrifuge test on clay model in the drum channelCentrifuge test on clay model in the drum channel

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25 30

over consolidation ratio OCR [-]

depth [mm]

0

20

40

60

80

100

120

140

160

-20 -15 -10 -5 0 5 10 15 20 25 30 35 40

undrained shear strength su [kPa]

depth [mm]

wt_v5_e1

wt_v5_e2_3_1

wt_v5_e2_3_2

wt_v5_e4_1

wt_v5_e4_2

calculated

constructed in flight at 60 g �� test at 50 g

= ⋅ ⋅ σb

u vs a OCR ' a = 0.24

b = 0.9

T-Bar-testing


Ground Improvement

Dr. Jan Laue


Stone column construction in the drum centrifugeStone column construction in the drum centrifugeStone column construction in the drum centrifugeStone column construction in the drum centrifuge

r

z

ω

θ

laser scanner

pore pressuretransducers

filling tube lost tip

r-z-workingtable

tool table

flexible sandhose

soil model

axes

drum channel


Ground Improvement

Dr. Jan Laue


Stone column installation toolStone column installation toolStone column installation toolStone column installation tool


Ground Improvement

Dr. Jan Laue


Model preparation in tub (2D) and drum (3D): placing column gridModel preparation in tub (2D) and drum (3D): placing column gridModel preparation in tub (2D) and drum (3D): placing column gridModel preparation in tub (2D) and drum (3D): placing column grid

area ratio of improvement - fs = 10% area ratio of improvement - fs = 5% & 10 %

COMPARE:

Unimproved (L)

v. Improved (R)


Ground Improvement

Dr. Jan Laue


Columns without compaction

34 mm

Columns built with additional

compaction, e.g. 15mm out – 10mm in

165 ???? Clay fills pores in the column

1.77 ± 0.0715 / 10 [mm]

481.50 ± 0.02nill

Relative density [%]Dry density of column[g/cm3]Densification


Ground Improvement

Dr. Jan Laue


34 mm

Different lengths of columns occur because of

different available lenght of the tube

α

ng

drum channel

tool table

driving area of working table 30x35

70

30 70

65

120

rotary coupling

35

15

3530dimension [cm]

10


Ground Improvement

Dr. Jan Laue


Building the embankment

34 mm


Ground Improvement

Dr. Jan Laue


29 30 31 32 33 34 35 36 37 38 39 40

0

5

10

15

20

25

30

35

40

time [min]

excess pore water pressure [kPa]

PPT 25mm

PPT 70mm

PPT 120mm

Installation effects: Excess pore water pressure during column Installation effects: Excess pore water pressure during column Installation effects: Excess pore water pressure during column Installation effects: Excess pore water pressure during column construction construction construction construction

(2D)(2D)(2D)(2D)

1

2 3

4

compaction

insertion

120 mm

depth of PPTGL

20mm

70 mm

25 mm

29 30 31 32 33 34 35 36 37 38 39 40

0

20

40

60

80

100

120

time [min]

penetration depth [mm]


Ground Improvement

Dr. Jan Laue


Installation effects: heave of clay surfaceInstallation effects: heave of clay surfaceInstallation effects: heave of clay surfaceInstallation effects: heave of clay surface

0 1 2 3 4 5 6 7 8 9 10 11 12

0

0.5

1

1.5

2

2.5

3surface heave [mm]

area ratio of ground improvement As / A

g [%]

data points of drum model

trend function of drum model

container model


Ground Improvement

Dr. Jan Laue


Installation effects: on clay structureInstallation effects: on clay structureInstallation effects: on clay structureInstallation effects: on clay structure

Zone 1 – sand penetrates the clay, mixing of

sand and clay - 2 mm thick

2 [mm]2

Zone 2 – high shear strain due to pile

installation - max. 2 mm thick

6

Zone 3 – high confining stresses and

densification after consolidation - 6 mm

Zone 4 – moderate confining stresses and no

measurable densification


Ground Improvement

Dr. Jan Laue


Installation effectsInstallation effectsInstallation effectsInstallation effects

Zone 1

Zone 2

Zone 3

ESEM pictures –

Environmental Scanning

Electron Microscopy

3.5 mm

50x


Ground Improvement

Dr. Jan Laue


ESEM picture of zone 1 ESEM picture of zone 1 ESEM picture of zone 1 ESEM picture of zone 1 –––– clay between sand grainsclay between sand grainsclay between sand grainsclay between sand grains

randomly oriented structure of the clay

150 µµµµm

800x

50x


Ground Improvement

Dr. Jan Laue


ESEM picture of zone 2 ESEM picture of zone 2 ESEM picture of zone 2 ESEM picture of zone 2 –––– clay close to sand grainsclay close to sand grainsclay close to sand grainsclay close to sand grains

orientation of clay particles due to high shear strain parallel to column axis

150 µµµµm

800x

50x


Ground Improvement

Dr. Jan Laue


ESEM picture of zone 3 and 4 ESEM picture of zone 3 and 4 ESEM picture of zone 3 and 4 ESEM picture of zone 3 and 4 –––– clay far away from sand grainsclay far away from sand grainsclay far away from sand grainsclay far away from sand grains

randomly oriented structure of the clay

150 µµµµm

800x

50x


Ground Improvement

Dr. Jan Laue


1.70

1.72

1.74

1.76

1.78

1.80

1.82

1.84

1.86

1.88

1.90

0 5 10 15 20 25 30 35

distance to pile axis [mm]dry bulk density [g/cm

3]

26

28

30

32

34

36

38

40

0 5 10 15 20 25 30 35

distance to pile axis [mm]

porosity [%]

Results from mercury intrusion porosimetry analysis of clayResults from mercury intrusion porosimetry analysis of clayResults from mercury intrusion porosimetry analysis of clayResults from mercury intrusion porosimetry analysis of clayedge of pile

edge of pile

hyperbolic trend function

zone 1 2 3 4 zone 1 2 3 4


Ground Improvement

Dr. Jan Laue


Section of soil model in the tub (2D)Section of soil model in the tub (2D)Section of soil model in the tub (2D)Section of soil model in the tub (2D)

34 mm 12 mm

100 mm

s

H


Ground Improvement

Dr. Jan Laue


0 200 400 600 800 1000 1200 14000

20

40

60

80

100

120

140

time [min]

pore w

ater pressure [kPa]

improved

not improved

25 mm

70 mm

120 mm

depth of PPTGL

1

3

2

1

2

3

unimproved

t90 = 401 min

improved

t90 = 99 min

acceleration of consoli-

dation by factor 4

Pore water pressures after embankment construction (2D)Pore water pressures after embankment construction (2D)Pore water pressures after embankment construction (2D)Pore water pressures after embankment construction (2D)

10 % reinforcement


Ground Improvement

Dr. Jan Laue


Section of soil model in the drumSection of soil model in the drumSection of soil model in the drumSection of soil model in the drum

100 mm

31 mm 12 mm


Ground Improvement

Dr. Jan Laue


Pore water pressures after embankment construction (3D)Pore water pressures after embankment construction (3D)Pore water pressures after embankment construction (3D)Pore water pressures after embankment construction (3D)

0 100 200 300 400 500 600 7000

10

20

30

40

50

60

70

80

90

100

110

time [min]

pore w

ater pressu

re [kPa]

0 100 200 300 400 500 600 7000

10

20

30

40

50

60

70

80

90

100

110

time [min]

pore w

ater pressu

re [kPa]

0 100 200 300 400 500 600 7000

10

20

30

40

50

60

70

80

90

100

110

time [min]

pore w

ater pressu

re [kPa]

sector 3 – 12%

sector 8 – 12%

sector 1 – unimp.

Sector 3: t90 = 34 min �� 2 months (prototype)



acceleration of consolidation by factor 10

120 mm

depth of PPT

75 mm

25 mm

50 mm


Ground Improvement

Dr. Jan Laue


0 200 400 600 800 1000 1200

0

1

2

3

4

5

6

7

8

time [min]

settlement [m

m]

improved

not improved

embankment height

35 mm lead balls

∆σ∆σ∆σ∆σ = 100 kPa

10 % area ratio of improvement

factor of settlement

reduction, n = 1.75

12

①

②

②

Weber, 2007

TimeTimeTimeTime----settlement curves after embankment construction (2D)settlement curves after embankment construction (2D)settlement curves after embankment construction (2D)settlement curves after embankment construction (2D)


Ground Improvement

Dr. Jan Laue


Ground Improvement of double porous

material

(AMGISS, Marie Curie EU program)

- Reuse of oben cast deposits

- 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)

Fresh landfill. (photograph M. Větrovský)

Centrifuge set Up

Modelled clay lumps

made from real material


Ground Improvement

Dr. Jan Laue


Stone columns placed in double porosity soils (2D)Stone columns placed in double porosity soils (2D)Stone columns placed in double porosity soils (2D)Stone columns placed in double porosity soils (2D)


Ground Improvement

Dr. Jan Laue


0 13 25 38 51

56

43.27272727

30.54545455

17.81818182

5.090909091

Distance [mm]

Distance [mm]

400-480

320-400

240-320

160-240

80-160

0-80

Pressure distribution under the foundation: Test D (7 sand columns)


Ground Improvement

Dr. Jan Laue


Heavy Tamping tool is based on rockfall tool (Chikatamarla et al. 2005)

70 cm

Strongbox

100 cm

Actuator

Gallery

Cushion material

Axis

Magnet

Guiding tube

Model „boulder“

micro concrete (steel)

Drum wall

Tool platform

r

θ

z

70 cm

Strongbox

100 cm

Actuator

Gallery

Cushion material

Axis

Magnet

Guiding tube

Model „boulder“

micro concrete (steel)

Drum wall

Tool platform

r

θ

z

Guiding tube

Boulder with

accelerometer cable

Cushion material

Gallery construction

Strongbox17 cm

17 cm

3.7 cm

Guiding tube

Boulder with

accelerometer cable

Cushion material


Strongbox17 cm

17 cm

3.7 cm

Ground Improvement by Heavy TampingGround Improvement by Heavy TampingGround Improvement by Heavy TampingGround Improvement by Heavy Tamping


Ground Improvement

Dr. Jan Laue


Guiding tube

Boulder with

accelerometer cable

Cushion material


Strongbox17 cm

17 cm

3.7 cm

Guiding tube

Boulder with

accelerometer cable

Cushion material


Strongbox17 cm

17 cm

3.7 cmRockfall on a layer of clay lumps

Heavy Tamping tool is based on rockfall tool (Chikatamarla et al. 2005)

Adaptions


Ground Improvement

Dr. Jan Laue


Heavy Tamping tool in use


Ground Improvement

Dr. Jan Laue


Erste Ergebnisse

Energy reached in 4 tests (for comparison, 1t falling

from 10m heigth equivalent to 100kJ)Net soil pressure vers settlement

Footprint of foundation: 3.2 model A 3.2 Model B

Without

improvement the

foundation reached

a net soil pressure

of 60kPa at a

reference

settlement of 15mm


Ground Improvement

Dr. Jan Laue


Thank you very much for your attention

Documents

Modelling of Ground Improvement in a Drum Centrifuge Modelling of