prediction of the reinforcement ground behavior with the vacuum consolidation method by triaxial...
TRANSCRIPT
Prediction of The Reinforcement Ground Behavior with
The Vacuum Consolidation Method by Triaxial Model Test & FE Analysis
H.Kawabata
Y.Tanabashi
Y.Jiang
T.ShionoT.Shiono
Nagasaki University
Maruyama Industry Co,LtdMaruyama Industry Co,Ltd
Soft ground
Fill
Soft ground
Vacuum pomp
P
Background of research
It forces the water draining away, and promotes
the consolidation
lateral flow upheaval of the ground
Fill construction
Field is constricted
Vacuum consolidation
It is possible to support rapid construction
It can suppress lateral flow and upheaval of the ground
However, the ground behavior is not clarified enough, and the design and the site management depend very on the experienced technique.
combination
Construction technique
Airtight + protection sheet
Vertical drain
Horizontal drain
Porous catchment tube
Vacuum pomp
flow of drainage
Fill construction
Soft ground
Different ground behaviors Vacuum consolidation Method
Soft ground
Vacuum consolidation Method
Soft ground
Vacuum consolidation Method
settlement settlement
Vertical drain
Vacuum pomp
side contraction
P
盛土施工
軟弱層
Fill
lateral flowupheaval upheaval
Fill construction
vacuum pressure
settlement
pore water pressure
inclination
drainage discharge
The purpose is to predict the ground behavior of fill construction by using VCM
Purpose of research
Simulation of VCM Numerical analysis
confirm the validity of modeling
simulate the fill construction by using VCMNumerical simulation
comparison
Measurement itemField investigation
※ VCM ； Vacuum Consolidation Method
Field investigation
Construction spot panorama
Outline of field investigation
Construction period
20 November. 2003 ～Improved area
About 3300m2
Improved depth
About 12m
Loading vacuum pressure
About -69kPa
17.6m17.6m
187m187m162162160160158158 166166164164
4th construction field
Cross section of field
Fill
-1.0m
-2.0m
-5.0m
-11.9m
Sand mat
Surface soil
Clay
Sandy cilt
Cilty clay
Center of field
2.4m
-5.1mS-1
-11.3mS-2
-13.0mS-3
8.0m
-3.5mP-1
-8.5mP-3
-5.2mP-2
Differential settlement gauge
Pore pressure meter
0.8m
Field end
Vacuum Consolidation Method
P
Vacuum pomp
Vertical drain
Fill construction by using VCM
FillP
Finite element (FEM)analysis
Outline of analysisVacuum Consolidation Method
The coupled analysis of soil and water
SEKIGUCHI ･ OTA model
force the water draining away, and promote the consolidation
could express deformation behavior of pore water flow
and soil skeleton at the same time
could express the dynamic behavior of clay ground
Model of analysis
70m8.8m
0.9m
11m
Surface soil
Clay 1
Clay２Clay３
Cilty clay 1
Cilty clay 2
Cilty clay 3
Cilty clay 4
Cilty clay 5
Cilty clay 6
Sand mat
Reinforcement part
Sandy cilt
Vertical drain
Thickness ： 0.004m
Drain pitch ： 0.8m
Boundary of drainage
（ It is set to the jointed part of vertical drain and horizontal drain ）When the pump operates
⇒ Water head is -69kPa When the pump stops
⇒ undrained
Input parameterDepth ( G
L-m )Name of soil
layerModel
γt
(kN/m3)IP
E
(MPa)
C
(MPa)
k
(cm/sec)
－ Fill Linear elastic 18.00 － 26.4 0 1.000×10-2
0.00 ～ 1.00 Sand mat Linear elastic 18.63 － 16.4 0 1.000×10-3
1.00 ～ 2.00 Surface soilSekiguchi ・ Ot
a16.67 78.6 － － 3.100×10-7
2.00 ～ 3.00 Clay 1Sekiguchi ・ Ot
a13.39 78.6 1.61 0.0120 3.100×10-7
3.00 ～ 4.00 Clay 2Sekiguchi ・ Ot
a13.61 62.7 2.84 0.0139 2.900×10-7
4.00 ～ 5.00 Clay 3Sekiguchi ・ Ot
a14.25 41.3 1.46 0.0169 2.500×10-7
5.00 ～ 5.50 Sandy cilt Linear elastic 17.65 － 8.08 0 1.000×10-4
5.50 ～ 7.00 Cilty clay 1Sekiguchi ・ Ot
a13.94 55.9 3.57 0.0254 1.300×10-7
7.00 ～ 8.00 Cilty clay 2Sekiguchi ・ Ot
a13.83 61.9 2.65 0.0206 2.600×10-7
8.00 ～ 9.00 Cilty clay 3Sekiguchi ・ Ot
a14.05 61.1 3.04 0.0267 2.000×10-7
9.00 ～ 10.00 Cilty clay 4Sekiguchi ・ Ot
a14.08 63.8 3.32 0.0276 4.400×10-7
10.00 ～ 11.00 Cilty clay 5Sekiguchi ・ Ot
a14.86 44.2 4.85 0.0370 2.000×10-7
11.00 ～ 11.90 Cilty clay 6Sekiguchi ・ Ot
a16.05 40.9 4.50 0.0343 8.700×10-8
Pore pressureanalysis (GL-8.50m)
field (GL-8.50m)
analysis (GL-5.20m)
field (GL-5.20m)
analysis (GL-3.50m)
field (GL-3.50m)
Reason:
→ It is thought that drainage was promoted in field
when the pump stopped, while undrained boundary is
set in analysis.
GL-3.5m
Settlement of the center field
As a whole, a similar tendency is shown.
However, the value of analysis exceeds the value of field as time passes.
analysis
field
Reason: Pore pressure (GL-3.50m) ; analysis < field (Fig.12Fig.12) → In analysis, vacuum pressure propagation was overestimated compared with field.
Surrounding displacementIt is the result after vacuum pump operates for 94 days.
analysis
field
A similar tendency
Surrounding displacement(cm)
The surrounding displacement of the ground
can be predicted.
Side displacementWithin reinforcement area It is the result after vacuum pump operates for 98 days.
A similar tendency
analysis
field
The side displacement of the ground can be predicted.
Vacuum Consolidation Method
P
Vacuum pomp
Vertical drain
Fill construction by using VCM
FillP
Numerical simulation
Outline of numerical simulation Actual achievement
Slow fill construction ： 3 ～ 5cm/day
Fill construction by using VCM ： 10 ～ 20cm/day
Rate of fill
Numerical simulationRate of fill
Pay attention to the loading period of vacuum pressure in before filling, while filling, and after filling.
Rapid fill construction ： 20cm/day
Fill construction by using VCM ： 50cm/day
Analytical caseRate of fill ： 20cm/day ～ Height of fill is 5m ～
case Period of filling （ day ） Periods after stopping filling（ day ）
1 25 360
Rate of fill ： 50cm/day ～ Vacuum pressure + Height of fill 5m～
case
Period of vacuum pressure （ day ）
Periods after stopping
vacuum pressure
（ day ）Before Filling After
2 －
10
－
3603 － 60
4 20 －5 20 60
Comparison
0
2
4
6
- 100
-50
0
0 20 40 60 80 100 120(day)経過日数
Period of filling
Period of Vacuum pressure
Pattern diagrams盛
土高
(m)
真空
圧(k
Pa)
盛土
高(m
)真
空圧
(kPa
)
Vacuum pressure (kPa)
Height of fill (m)
5m
25days
case1
360 days after filling
5m
case2
10days
-69kPa
360 days after filling
case5
-69kPa
20days 30days
5m
90days
360 days after filling
Settlement in the center field
Rate of fill ： 20cm/day
In comparison with case1 and case5
The effect of the fill construction by using VCM is confirmed.
case1
case2
case5
Fill Vacuum pressure
case1case2
case5
Rate of fill ： 50cm/day Rebound occurs after the vacuum pump stopped.
In comparison with case2 and case5
It is thought that the influence of period of vacuum pressure is small.
It is result after filling or vacuum pump stopped after 360 days.In comparison with case2 and case5
It is thought that the influence of the period of vacuum pressure is small.
Surrounding displacement
Within reinforcement area
Surrounding displacement(cm)
case1
case2
case5
the center field
In comparison with case1 and case2 , case5
The suppressive effect to upheaval of the ground by the VCM is confirmed.
Within reinforcement area
Side displacement
case1
case2
case5
It is result after filling or vacuum pump stopped after 360 days.In comparison with case1 and case2 , case5
The suppressive effect to lateral flow by the VCM is confirmed.
The numerical analysis is able to reflect the behavior of field using VCM.
Conclusion ①
comparison
Field investigation
The agreement was confirmed from the results of the Numerical analysis and Value of field
on the items of pore pressure, settlement, surrounding displacement and side displacement.
Numerical analysis
Conclusion ②
The suppressive effect to lateral flow and upheaval
of the ground by the VCM has been confirmed.
Numerical simulation
It is able to predict the behavior of field
in fill construction by using VCM.
謝々謝々
Experimental apparatus
Triaxial room
Displacement meter
Load cell
Control panel
triaxial room
Pore pressure meter
Drain
diameter ： 7.4cm
height ： 15cm
Specimen
lateral pressure
axial pressure
Initial conditionIt loads axial pressure and
lateral pressure
Excess pore pressure loss
axial displacement, drainage discharge,
and pore water pressure
Automatic measuring
water
The vacuum pressure (-69kPa) is loaded
Outline of triaxial test
：Specimen
T‐7
T‐3
T-6
T-9
GL-5.0m
GL-2.0m
GL-7.0m
GL-9.0m
GL-12.0m
3m
2m
2m
3m
Way of reduction
-100
-80
-60
-40
-20
0
0 10 20 30 40 50
Time(day）
Settl
emen
t（㎝
）
settlement ＝ Σ （ axial strain ×each thickness of the ground ）
Model test
Field(center)
Field （ avarage ）
Settlement
0
500
1000
1500
2000
2500
3000
3500
0 10 20 30 40 50Time（day)
Dri
anag
e d
isch
arge
（m3 ）
Model test
drainage discharge
＝ Σ （ bulk strain ×area ×thickness of the ground ）
Field
Drainage discharge
Field （ GL-3.5m ）Model （ T-3 ）
Model （ T-7 ）
Field （ GL-8.5m ）
Pore water pressure Time (day)
Por
e w
ater
pre
ssur
e(kP
a)
Constitutive(SEKIGUCHI ･ OTA model)
Yield function
*
0
D'p
'plnMDf
初期状態の偏差応力
偏差応力
初期状態の有効応力
有効応力
ここに
:S
:S
:'p
:'p
'p
S
'p
S
'p
S
'p
S
2
3,
0ij
ij
0
0
0ijij
0
0ijij*
M =
)1(
'sin3
'sin6
)1( 0
e
M : Limit strain ratio
D : dalitancy coefficient
パラメータ決定フロー ( 関口・太田モデル )
限界応力比
ダイレイタンシー係数
非可逆比先行圧密時の静止土圧係数有効応力に基づくポアソン比
c
0
0
0
0
p2
0
p
C434.0
,
e1MD
K1
K'
'sin1K
I1042.044.0K
75.1
M
Ilog233.081.0sin
,
sin3
'sin6M
ここに
Λ
Λ
ここに
塑性指数