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