Treasure’s report of1st Lizzi Scholarship
Shingo MORIMASAGraduate Student, GeoMechanics Group,
Toyohashi University of Technology
IWM2006 in Schrobenhausen, Germany: May 5th, 2006
Treasure’s Report
38,500 YEN ($351.41)TOTAL
8,190 yenRail fare from Tokyo to Toyohashi
190 yenRail fare from Oyamadai to Oimachi
360 yenRail fare from Kachidoki to Denen-chofu
19,080 yenLodging charge for three nights
2004/08/27
710 yenRail fare from Negishi to Kachidoki
360 yenRail fare from Kachidoki to Denen-chofu2004/08/26
410 yenRail fare from Denen-chofu to Kachidoki
410 yenRail fare from Kachidoki to Denen-chofu2004/08/25
600 yenRail fare from Shibuya to Kachidoki
8,190 yenRail fare from Toyohashi to Tokyo2004/08/24
TotalType of ExpenseDate
1st Lizzi Scholarship (IWM2004)
Simulation of the Confining Effect onBearing Capacity of Micropile Foundation;-- Field Loading Test and FEM Simulation --
Shingo MORIMASAGraduate Student, GeoMechanics Group,
Toyohashi University of Technology
IWM2006 in Schrobenhausen, Germany: May 5th, 2006
Table of contentsPurposeField Loading Test
Prestressed micropile method
FEM simulationConfining effectEffects of network and prestress
Summary and future plan
The purpose of this studyEarly studies (Otani, Tsukada, Miura et al)
“Model Loading Tests on The Footing Reinforced with Prestressed Micropiles”“Large-Scaled Field Loading Test on The Footing Reinforced with Prestressed Micropiles”
Analytic clarification of the mechanism of the mobilization of load bearing capacity of foundation reinforced with prestressedmicropiles
Field loading test
The boring log and the SPT N-value of the upper 10 meters
The subsoils are fill, loam, cemented clay, sandy clay, and fine sand, respectively.
The fill, loam and clay are soft; the SPT N-values are less than 5.
(a) S-MP (b) FT-MP/FT-PSMP
The micropile is 3 m long, 100 mm in diameter, with a steel bar of 32 mm in diameter
Field loading test
Loading apparatus
Vertical Loading test Horizontal Loading test
The results of vertical loading tests
Initial coefficient of subgrade reaction
FT-MP(non-prestressed)1.86×104kN/m3
FT-PSMP(prestressed)3.97×104kN/m3
300
250
200
150
100
50
00 100 200 300 400 500 600 700
FT FT+8MPs FT-MP
FT-PSMP
Settl
emen
t, S
(mm
)
Load (kN)
FT-PSMP: prestressed
FT-MP: non-prestressed
FT+8MPs:Summation of footing and8 micropiles
Also in field loading test, network effect was mobilized.The settlement became half due to the effect of prestress.
The results of horizontal loading tests
30
25
20
15
10
5
00 5 10 15 20 25 30
FT-MP
FT-PSMP
Hor
izon
tal d
ispl
acem
ent (
mm
)
Horizontal load (kN)
Initial coefficient of subgrade reaction
FT-MP(non-prestressed)1.01 ×103kN/m3
FT-PSMP(prestressed)17.1×103kN/m3
FT-PSMP: prestressed
FT-MP: non-prestressed
The effect of prestress was significant in the horizontalmovement control.
FEM simulationFooting:
rigid material
Micropiles:elastic bending material
second-order FEM elements
Ground:elasto-plastic model
Drucker-Prager Type
Ground - Micropiles:bi-linear slider element
Analysis condition
Type of foundationFooting, Micropile(MP), MP-footing, and prestressed MP-footing
GroundDense sand and Loose sand
LoadingVertical and Horizontal Loading
Input parameters
Mechanical properties
Frinction angle between Ground and Micropiles
Internal friction angle of ground tanφ
PrestressApproximately 30% of bearing capacity of micropiles
0.31.20×1081.04×1082.00×10310035Dense sand
0.30.40×1080.35×1081.90×103-10030Loose sand
2.40×103
ρ (kg/m3)
70×108
E (N/m2)ψ (°)
2.69×109
G (N/m2)
0.3Micropile
νc (N/m2)φ (°)
Dilatancy angleψ > 0 :positive dilatancyψ < 0 :negative dilatancy
123
307
FT-MP
1.24993564Loose sand
1.8216945124Dense sand
RFT+MPs
+
MPFTCritical load
bearing capacity+
0.06
0.05
0.04
0.03
0.02
0.01
0.000 50 100 150 200
Footing(FT) Micropile(MP) MP footing(FT-MP)
Load, q (kN)
Dis
plac
emen
t, S
(m)
Loose Sand Ground
0.06
0.05
0.04
0.03
0.02
0.01
0.000 100 200 300 400
Load, q (kN)
Dis
plac
emen
t, S
(m)
Dense Sand Ground
Vertical Loading Condition
FT+MPs FT+MPs
R= FT-MPFT+MPs
Network effect index
(Confining Effect)
Vertical Loading Condition
20000
156
FT-PSMP
19000
123
FTMP
Initial Coefficientof subgrade reaction
Critical bearing capacity
31000
436
FT-PSMP
31000
307
FTMP
0.06
0.05
0.04
0.03
0.02
0.01
0.000 50 100 150 200
with prestress without prestress
Load, q (kN)
Dis
plac
emen
t, S
(m)
Loose Sand Ground
0.06
0.05
0.04
0.03
0.02
0.01
0.000 100 200 300 400 500
Load, q (kN)
Dis
plac
emen
t, S
(m)
Dense Sand Ground
Loose sand Dense sand
(Effect of prestress)
0.06
0.05
0.04
0.03
0.02
0.01
0.000 10 20 30 40 50
Load, q (kN)
Dis
plac
emen
t, S
(m)
Loose Sand Ground
MP(
Mic
ropi
le)
0.06
0.05
0.04
0.03
0.02
0.01
0.000 10 20 30 40 50 60 70 80
MP(
Mic
ropi
le)
with prestress without prestress
Load, q (kN)
Dis
plac
emen
t, S
(m)
Dense Sand Ground
Horizontal Loading Condition
650
38
FT-PSMP
630
23
FTMP
Initial Coefficientof subgrade reaction
Critical bearing capacity
820
67
FT-PSMP
760
31
FTMP
Loose sand Dense sand
(Effect of prestress)
Summary and future planThe confining effects on the ground by the micropiles were clearly observed both in the loading tests and FEM simulationsThe effect of the prestress which induced the confinement on the subsoil by the footing and the micropiles, was recognized not only in the loading tests but also in the FEM simulations.
The FEM simulation must be modifiedThe yielding of micropiles under the horizontal loading on pilesThe increase in shear modulus of ground due to the confinement
3-D FEM simulationnetwork of micropilesconfining effect
Thank you for your attention !
End of the Presentation
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