Applications of PARI centrifuge model tests, Mazaki Kitazume

Applications of PARI 

centrifuge Model tests 

Masaki KITAZUME 

Port and Airport Research Institute 

August 4, 2003 The 12th Asian Regional Conference 1

Practical research having close 

relevance to specific prototype 

- Haneda Offshore Expansion Project - 

May, 1990 August, 1998 


Reclamation and Dredging 

History of Haneda Site 

(1) before 

1965 

(2) 1965- 

1970 

(3) 1971- 

1981 

(4) after 

1981 

AP+1m 

AP-10 

~-20m 

AP-20 

~-38m 

As1 

Ac2 

Dc1 

As1 

Ac2 

Dc1 

Ac1 

As1 

Ac2 

Dc1 

Bs 

Ac1 

As1 

Ac2 

Dc1 


application of fabripacked 

sand drain 

The clay layer at the construction site 

had high water content exceeding 150% 

( being metaphorically called as 

“Haneda Mayonnaise Layer”) 

Sand piles was not able to stand 

and in soft clay and might fail to 

function as drainage path. 


fabri-packed drain 

Fabri-packed sand drain 

• sand drain wrapped by an 

envelope made of geotextile 

• expected to stabilize the sand 

pile to function as a drainage 

path in soft ground. 


modeling in centrifuge 

prototype 

model 

50cm 

Cement treated soil 

(Ac1) 

soft clay deposit 

(Ac1) 

clay deposit 

(Ac2) 

Sand deposit 

10.9cm 


preparation of 

model sand pile 

control density 

by vibration 

frozen and 

extract by motor jack 


preparation of 

model ground 

• preparing the bottom sand layer 

• preparing the lower clay layer 

compressed one dimensionally to a 

vertical effective stress of 30 kN/m 2 . 

• install fabri-packed sand drain in frozen 

condition on the lower clay layer. 

• pore saturated clay slurry at a water 

content of 150%. 

• place a perspex doughnut plate at clay 

surface to simulate cement-treated soil. 

• place Toyoura sand and lead shot as fill 

materials. 


time – settlement curves 

settlement (mm) 

0 

20 

40 

60 

80 

100 

1 10 100 1000 10000 

time (min) 

The two curves obtained at the top of 

sand pile and at the clay surface coincide 

during the consolidation, which shows 

no differential settlement took place in 

the composite ground consisting soft 

clay and a sand pile. 


deformation 

of sand pile 

settlement (mm) 

0 

20 

40 

60 

80 

(1) (2) 

(6) 

(3) 

(4) 

(5) 

(6) 

100 

1 10 100 1000 10000 

time (min) 

(1) (2) (3) (4) (5) 


time – earth pressure 

curves 

earth pressure (kN/m 2 ) 

250 

200 

150 

100 

100 

1 10 100 1000 10000 

time (min) 

pressure (kN/m 2 ) 

2 4 6 

effective 

stress 

hydro-static 

stress 

The pressure distribution changes during 

consolidation process. 

August 4, 2003 The 12th Asian Regional Conference 11 

200 

100 

0 

U= 0% 

U=50% 

U=90% 

sand 

pile 

total stress

tensile rigidity – stress 

concentration ratio 

stress concentration ratio 

4.0 

3.0 

2.0 

1.0 

1 100 200 300 

tensile rigidity of geotextile (N/5cm/%) 

Stress concentration 

ratio increased almost 

linearly with the tensile 

rigidity of geotextile 


tensile rigidity – stress 

concentration ratio 

stress concentration ratio 

4.0 

3.0 

2.0 

1.0 

1 100 200 300 

tensile rigidity (N/5cm/%) 

The influence of the stress concentration 

on the consolidation settlement: 

β = 1 / (As * n + (1 - As)) 

where: 

β: ratio of the settlement of an improved 

ground against that of un-improved 

ground 

n : stress concentration ratio 

As : replacement area ratio 

The decrease of the settlement 

remained within 5 % as long as the 

tensile rigidity was lower than about 

200N/5cm/%. 


conclusion of model test 

• The study revealed that the geotextile functions well to stabilize 

the sand pile in the extremely soft clay ground. The stress 

concentration resulting from the tensile rigidity of the geotextiles 

evaluated was smaller than anticipated and might not cause 

undesirable settlement. 

• As the applicability of the fabripacked 

sand drain was confirmed 

by the centrifuge model 

study, the method was 

employed in the Haneda 

Project. 


Conclusions 

• PARI centrifuge has been employed extensively to 

investigate not only on basic research topics but 

also on practical topics. The research results have 

been applied to constructions of various port and 

airport facilities. 

• Challenging but fairly 

difficult field on centrifuge 

application will be one to 

the major subjects of the 

PARI centrifuge. 

swing platform 

main arm 

main shaft 


esearch subjects (1) 

• curiosity oriented and fundamental research 

bearing capacity of sand and clay 

reinforcement by geotextile 

pile foundation 

sand drain method 

sand compaction pile method 

deep mixing method 

development of earthquake simulator 


Curiosity oriented and 

fundamental research 

- Development of design formula for 

SCP improved ground - 


Bearing capacity 

shear strength of SCP improved ground: 

τ=(1-as) (C 0 + k・z + μc・Δσz ・Cu/p ・ U) + 

(γs ・ z +μs ・ Δσz ) ・ as ・ tan φs ・cos 2θ 

clay 

embankment 

sand pile 

where 

τ: shear strength 

as: improvement area ratio 

C 0 

+ kz : undrained shear strength of clay 

μs : coefficient of stress concentration 

Δσz : increment of vertical stress due to 

external load 

n : stress concentration ratio 

U :average degree of consolidation of clay in 

between sand piles 

φs : friction angle of sand pile 

γs : unit weight of sand pile 


preparation of model 

ground 

Solenoid 

valve 

Caisson 

Loading Jack 

LVDT 

Load Cell 

35cm 10cm 

loading procedure 

Vertical load was 

applied by quick lowering 

of the water level. 

Horizontal load was 

applied immediately after 

that by means of the 

horizontal loading jack. 

50cm 


preparation of model 

ground 

pre-consolidation in laboratory 

installation of sand piles 


load – displacement 

carves 

1.2 

Vertical Loading 

Horizontal Loading 

vertical load, V (kN) 

1.0 

0.8 

0.6 

0.4 

0.2 

1st stage load 

0 

0 10 20 30 

settlement, S (mm) 

horizontal load, H (kN) 

0.15 

0.10 

0.05 

V=0.29kN 

V=0.45kN 

V=0.1kN 

0 

0 4 8 1.2 

horizontal displacement, dh (mm) 


ground failure 

in vertical loading 

ground deformation 

failure pattern of sand piles 


failure envelope 

horizontal load, H (kN) 

0.15 

0.10 

0.05 

Calculation 

0 

0 0.2 0.4 0.6 0.8 

vertical load, V (kN) 

Bearing capacity of the 

improved ground can be 

estimated by a simple 

clip circle method 

combined with the 

practical formula for the 

shear strength of 

composite ground. 


field test at Maizuru Port 

Maizuru Port 

Tokyo 

Osaka 

steel tank 

L.WL.+0.00 

caisson 

Purpose: 

to establish design method 

for low as improvement. 

Procedure: 

SCP improved ground is 

subjected to vertical load to 

fail 

SCP φ1.7m 

SCP φ2.0m 

-10 

-15 

-20 


load – settlement curve 

settlement (cm) 

80 

100 

120 

140 

vertical load (kN/m 2 ) 

90 100 110 

6:30 

7:45 

6:45 

7:15 

8:00 

At 6:45 the concrete caisson is 

filled up with water and the 

loading is once interrupted for 

changing pipelines from the 

caisson to the tank. 

The yield load of ground is 

determined as 106 kNm 2 . 


failure pattern 

steel tank 

caisson 

SCP 

25% 75% 

-6m 

-10m 

-14m 

-18m 

-22m 


Conclusion of the test 

• Bearing capacity of the improved ground can be 

estimated by a simple slip circle method of stability 

analysis combined with the practical formula for the 

shear strength of composite ground. 


esearch subjects (2) 

• practical research having close relevance to 

specific prototype 

Niigata Port (application of DMM to retaining wall) 

Haneda Airport (Stability of retaining wall during 

excavation, application of fabri-packed sand drain, influence 

of embedded sheet pile wall to deformation of ground 

surface) 

Wakayama Shimotsu Port (effect of local soil DMM 

improvement) 

Osaka Port (effect of SCP improvement on slope stability) 

Kumamoto Port (Deformation of soft ground under 

placement of soft-loading breakwater)

Applications of PARI centrifuge model tests, Mazaki Kitazume

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