Applications of PARI centrifuge model tests, Mazaki Kitazume
Applications of PARI centrifuge model tests, Mazaki Kitazume
Applications of PARI centrifuge model tests, Mazaki Kitazume
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<strong>Applications</strong> <strong>of</strong> <strong>PARI</strong><br />
<strong>centrifuge</strong> Model <strong>tests</strong><br />
Masaki KITAZUME<br />
Port and Airport Research Institute<br />
August 4, 2003 The 12th Asian Regional Conference 1
Practical research having close<br />
relevance to specific prototype<br />
- Haneda Offshore Expansion Project -<br />
May, 1990 August, 1998<br />
August 4, 2003 The 12th Asian Regional Conference 2
Reclamation and Dredging<br />
History <strong>of</strong> Haneda Site<br />
(1) before<br />
1965<br />
(2) 1965-<br />
1970<br />
(3) 1971-<br />
1981<br />
(4) after<br />
1981<br />
AP+1m<br />
AP-10<br />
~-20m<br />
AP-20<br />
~-38m<br />
As1<br />
Ac2<br />
Dc1<br />
As1<br />
Ac2<br />
Dc1<br />
Ac1<br />
As1<br />
Ac2<br />
Dc1<br />
Bs<br />
Ac1<br />
As1<br />
Ac2<br />
Dc1<br />
August 4, 2003 The 12th Asian Regional Conference 3
application <strong>of</strong> fabripacked<br />
sand drain<br />
The clay layer at the construction site<br />
had high water content exceeding 150%<br />
( being metaphorically called as<br />
“Haneda Mayonnaise Layer”)<br />
Sand piles was not able to stand<br />
and in s<strong>of</strong>t clay and might fail to<br />
function as drainage path.<br />
August 4, 2003 The 12th Asian Regional Conference 4
fabri-packed drain<br />
Fabri-packed sand drain<br />
• sand drain wrapped by an<br />
envelope made <strong>of</strong> geotextile<br />
• expected to stabilize the sand<br />
pile to function as a drainage<br />
path in s<strong>of</strong>t ground.<br />
August 4, 2003 The 12th Asian Regional Conference 5
<strong>model</strong>ing in <strong>centrifuge</strong><br />
prototype<br />
<strong>model</strong><br />
50cm<br />
Cement treated soil<br />
(Ac1)<br />
s<strong>of</strong>t clay deposit<br />
(Ac1)<br />
clay deposit<br />
(Ac2)<br />
Sand deposit<br />
10.9cm<br />
August 4, 2003 The 12th Asian Regional Conference 6
preparation <strong>of</strong><br />
<strong>model</strong> sand pile<br />
control density<br />
by vibration<br />
frozen and<br />
extract by motor jack<br />
August 4, 2003 The 12th Asian Regional Conference 7
preparation <strong>of</strong><br />
<strong>model</strong> ground<br />
• preparing the bottom sand layer<br />
• preparing the lower clay layer<br />
compressed one dimensionally to a<br />
vertical effective stress <strong>of</strong> 30 kN/m 2 .<br />
• install fabri-packed sand drain in frozen<br />
condition on the lower clay layer.<br />
• pore saturated clay slurry at a water<br />
content <strong>of</strong> 150%.<br />
• place a perspex doughnut plate at clay<br />
surface to simulate cement-treated soil.<br />
• place Toyoura sand and lead shot as fill<br />
materials.<br />
August 4, 2003 The 12th Asian Regional Conference 8
time – settlement curves<br />
settlement (mm)<br />
0<br />
20<br />
40<br />
60<br />
80<br />
100<br />
1 10 100 1000 10000<br />
time (min)<br />
The two curves obtained at the top <strong>of</strong><br />
sand pile and at the clay surface coincide<br />
during the consolidation, which shows<br />
no differential settlement took place in<br />
the composite ground consisting s<strong>of</strong>t<br />
clay and a sand pile.<br />
August 4, 2003 The 12th Asian Regional Conference 9
deformation<br />
<strong>of</strong> sand pile<br />
settlement (mm)<br />
0<br />
20<br />
40<br />
60<br />
80<br />
(1) (2)<br />
(6)<br />
(3)<br />
(4)<br />
(5)<br />
(6)<br />
100<br />
1 10 100 1000 10000<br />
time (min)<br />
(1) (2) (3) (4) (5)<br />
August 4, 2003 The 12th Asian Regional Conference 10
time – earth pressure<br />
curves<br />
earth pressure (kN/m 2 )<br />
250<br />
200<br />
150<br />
100<br />
100<br />
1 10 100 1000 10000<br />
time (min)<br />
pressure (kN/m 2 )<br />
2 4 6<br />
effective<br />
stress<br />
hydro-static<br />
stress<br />
The pressure distribution changes during<br />
consolidation process.<br />
August 4, 2003 The 12th Asian Regional Conference 11<br />
200<br />
100<br />
0<br />
U= 0%<br />
U=50%<br />
U=90%<br />
sand<br />
pile<br />
total stress
tensile rigidity – stress<br />
concentration ratio<br />
stress concentration ratio<br />
4.0<br />
3.0<br />
2.0<br />
1.0<br />
1 100 200 300<br />
tensile rigidity <strong>of</strong> geotextile (N/5cm/%)<br />
Stress concentration<br />
ratio increased almost<br />
linearly with the tensile<br />
rigidity <strong>of</strong> geotextile<br />
August 4, 2003 The 12th Asian Regional Conference 12
tensile rigidity – stress<br />
concentration ratio<br />
stress concentration ratio<br />
4.0<br />
3.0<br />
2.0<br />
1.0<br />
1 100 200 300<br />
tensile rigidity (N/5cm/%)<br />
The influence <strong>of</strong> the stress concentration<br />
on the consolidation settlement:<br />
β = 1 / (As * n + (1 - As))<br />
where:<br />
β: ratio <strong>of</strong> the settlement <strong>of</strong> an improved<br />
ground against that <strong>of</strong> un-improved<br />
ground<br />
n : stress concentration ratio<br />
As : replacement area ratio<br />
The decrease <strong>of</strong> the settlement<br />
remained within 5 % as long as the<br />
tensile rigidity was lower than about<br />
200N/5cm/%.<br />
August 4, 2003 The 12th Asian Regional Conference 13
conclusion <strong>of</strong> <strong>model</strong> test<br />
• The study revealed that the geotextile functions well to stabilize<br />
the sand pile in the extremely s<strong>of</strong>t clay ground. The stress<br />
concentration resulting from the tensile rigidity <strong>of</strong> the geotextiles<br />
evaluated was smaller than anticipated and might not cause<br />
undesirable settlement.<br />
• As the applicability <strong>of</strong> the fabripacked<br />
sand drain was confirmed<br />
by the <strong>centrifuge</strong> <strong>model</strong><br />
study, the method was<br />
employed in the Haneda<br />
Project.<br />
August 4, 2003 The 12th Asian Regional Conference 14
Conclusions<br />
• <strong>PARI</strong> <strong>centrifuge</strong> has been employed extensively to<br />
investigate not only on basic research topics but<br />
also on practical topics. The research results have<br />
been applied to constructions <strong>of</strong> various port and<br />
airport facilities.<br />
• Challenging but fairly<br />
difficult field on <strong>centrifuge</strong><br />
application will be one to<br />
the major subjects <strong>of</strong> the<br />
<strong>PARI</strong> <strong>centrifuge</strong>.<br />
swing platform<br />
main arm<br />
main shaft<br />
August 4, 2003 The 12th Asian Regional Conference 15
esearch subjects (1)<br />
• curiosity oriented and fundamental research<br />
bearing capacity <strong>of</strong> sand and clay<br />
reinforcement by geotextile<br />
pile foundation<br />
sand drain method<br />
sand compaction pile method<br />
deep mixing method<br />
development <strong>of</strong> earthquake simulator<br />
August 4, 2003 The 12th Asian Regional Conference 16
Curiosity oriented and<br />
fundamental research<br />
- Development <strong>of</strong> design formula for<br />
SCP improved ground -<br />
August 4, 2003 The 12th Asian Regional Conference 17
Bearing capacity<br />
shear strength <strong>of</strong> SCP improved ground:<br />
τ=(1-as) (C 0 + k・z + μc・Δσz ・Cu/p ・ U) +<br />
(γs ・ z +μs ・ Δσz ) ・ as ・ tan φs ・cos 2θ<br />
clay<br />
embankment<br />
sand pile<br />
where<br />
τ: shear strength<br />
as: improvement area ratio<br />
C 0<br />
+ kz : undrained shear strength <strong>of</strong> clay<br />
μs : coefficient <strong>of</strong> stress concentration<br />
Δσz : increment <strong>of</strong> vertical stress due to<br />
external load<br />
n : stress concentration ratio<br />
U :average degree <strong>of</strong> consolidation <strong>of</strong> clay in<br />
between sand piles<br />
φs : friction angle <strong>of</strong> sand pile<br />
γs : unit weight <strong>of</strong> sand pile<br />
August 4, 2003 The 12th Asian Regional Conference 18
preparation <strong>of</strong> <strong>model</strong><br />
ground<br />
Solenoid<br />
valve<br />
Caisson<br />
Loading Jack<br />
LVDT<br />
Load Cell<br />
35cm 10cm<br />
loading procedure<br />
Vertical load was<br />
applied by quick lowering<br />
<strong>of</strong> the water level.<br />
Horizontal load was<br />
applied immediately after<br />
that by means <strong>of</strong> the<br />
horizontal loading jack.<br />
50cm<br />
August 4, 2003 The 12th Asian Regional Conference 19
preparation <strong>of</strong> <strong>model</strong><br />
ground<br />
pre-consolidation in laboratory<br />
installation <strong>of</strong> sand piles<br />
August 4, 2003 The 12th Asian Regional Conference 20
load – displacement<br />
carves<br />
1.2<br />
Vertical Loading<br />
Horizontal Loading<br />
vertical load, V (kN)<br />
1.0<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
1st stage load<br />
0<br />
0 10 20 30<br />
settlement, S (mm)<br />
horizontal load, H (kN)<br />
0.15<br />
0.10<br />
0.05<br />
V=0.29kN<br />
V=0.45kN<br />
V=0.1kN<br />
0<br />
0 4 8 1.2<br />
horizontal displacement, dh (mm)<br />
August 4, 2003 The 12th Asian Regional Conference 21
ground failure<br />
in vertical loading<br />
ground deformation<br />
failure pattern <strong>of</strong> sand piles<br />
August 4, 2003 The 12th Asian Regional Conference 22
failure envelope<br />
horizontal load, H (kN)<br />
0.15<br />
0.10<br />
0.05<br />
Calculation<br />
0<br />
0 0.2 0.4 0.6 0.8<br />
vertical load, V (kN)<br />
Bearing capacity <strong>of</strong> the<br />
improved ground can be<br />
estimated by a simple<br />
clip circle method<br />
combined with the<br />
practical formula for the<br />
shear strength <strong>of</strong><br />
composite ground.<br />
August 4, 2003 The 12th Asian Regional Conference 23
field test at Maizuru Port<br />
Maizuru Port<br />
Tokyo<br />
Osaka<br />
steel tank<br />
L.WL.+0.00<br />
caisson<br />
Purpose:<br />
to establish design method<br />
for low as improvement.<br />
Procedure:<br />
SCP improved ground is<br />
subjected to vertical load to<br />
fail<br />
SCP φ1.7m<br />
SCP φ2.0m<br />
-10<br />
-15<br />
-20<br />
August 4, 2003 The 12th Asian Regional Conference 24
load – settlement curve<br />
settlement (cm)<br />
80<br />
100<br />
120<br />
140<br />
vertical load (kN/m 2 )<br />
90 100 110<br />
6:30<br />
7:45<br />
6:45<br />
7:15<br />
8:00<br />
At 6:45 the concrete caisson is<br />
filled up with water and the<br />
loading is once interrupted for<br />
changing pipelines from the<br />
caisson to the tank.<br />
The yield load <strong>of</strong> ground is<br />
determined as 106 kNm 2 .<br />
August 4, 2003 The 12th Asian Regional Conference 25
failure pattern<br />
steel tank<br />
caisson<br />
SCP<br />
25% 75%<br />
-6m<br />
-10m<br />
-14m<br />
-18m<br />
-22m<br />
August 4, 2003 The 12th Asian Regional Conference 26
Conclusion <strong>of</strong> the test<br />
• Bearing capacity <strong>of</strong> the improved ground can be<br />
estimated by a simple slip circle method <strong>of</strong> stability<br />
analysis combined with the practical formula for the<br />
shear strength <strong>of</strong> composite ground.<br />
August 4, 2003 The 12th Asian Regional Conference 27
esearch subjects (2)<br />
• practical research having close relevance to<br />
specific prototype<br />
Niigata Port (application <strong>of</strong> DMM to retaining wall)<br />
Haneda Airport (Stability <strong>of</strong> retaining wall during<br />
excavation, application <strong>of</strong> fabri-packed sand drain, influence<br />
<strong>of</strong> embedded sheet pile wall to deformation <strong>of</strong> ground<br />
surface)<br />
Wakayama Shimotsu Port (effect <strong>of</strong> local soil DMM<br />
improvement)<br />
Osaka Port (effect <strong>of</strong> SCP improvement on slope stability)<br />
Kumamoto Port (Deformation <strong>of</strong> s<strong>of</strong>t ground under<br />
placement <strong>of</strong> s<strong>of</strong>t-loading breakwater)<br />
August 4, 2003 The 12th Asian Regional Conference 28