Treasure s report of 1 st Lizzi Scholarship IWM2006 in - - PowerPoint PPT Presentation

Treasure’s report of 1st Lizzi Scholarship

Shingo MORIMASA

Graduate 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 yen Rail fare from Tokyo to Toyohashi 190 yen Rail fare from Oyamadai to Oimachi 360 yen Rail fare from Kachidoki to Denen-chofu 19,080 yen Lodging charge for three nights 2004/08/27 710 yen Rail fare from Negishi to Kachidoki 360 yen Rail fare from Kachidoki to Denen-chofu 2004/08/26 410 yen Rail fare from Denen-chofu to Kachidoki 410 yen Rail fare from Kachidoki to Denen-chofu 2004/08/25 600 yen Rail fare from Shibuya to Kachidoki 8,190 yen Rail fare from Toyohashi to Tokyo 2004/08/24 Total Type of Expense Date

1st Lizzi Scholarship (IWM2004)

Simulation of the Confining Effect on Bearing Capacity of Micropile Foundation;

• - Field Loading Test and FEM Simulation --

Shingo MORIMASA

Graduate Student, GeoMechanics Group, Toyohashi University of Technology

IWM2006 in Schrobenhausen, Germany: May 5th, 2006

Table of contents

Purpose Field Loading Test

Prestressed micropile method

FEM simulation

Confining effect Effects of network and prestress

Summary and future plan

The purpose of this study

Early 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

• f foundation reinforced with prestressed

micropiles

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 50 100 200 300 400 500 600 700

FT

FT+8MPs FT-MP FT-PSMP Settlement, S (mm) Load (kN) FT-PSMP: prestressed FT-MP: non-prestressed FT+8MPs: Summation of footing and 8 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 5 10 15 20 25 30

FT-MP FT-PSMP

Horizontal displacement (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 horizontal movement control.

FEM simulation

Footing:

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 foundation

Footing, Micropile(MP), MP-footing, and prestressed MP-footing

Ground

Dense sand and Loose sand

Loading

Vertical and Horizontal Loading

Input parameters

Mechanical properties Frinction angle between Ground and

Micropiles

Internal friction angle of ground tanφ

Prestress

Approximately 30% of bearing capacity of

micropiles

0.3 1.20×108 1.04×108 2.00×103 10 35 Dense sand 0.3 0.40×108 0.35×108 1.90×103

• 10

30 Loose sand 2.40×103 ρ (kg/m3) 70×108 E (N/m2) ψ (°) 2.69×109 G (N/m2) 0.3 Micropile ν c (N/m2) φ (°)

Dilatancy angle

ψ > 0 :positive dilatancy ψ < 0 :negative dilatancy

123 307

FT-MP

1.24 99 35 64 Loose sand 1.82 169 45 124 Dense sand

R FT+MPs + MP FT

Critical load bearing capacity

+

0. 06 0. 05 0. 04 0. 03 0. 02 0. 01 0. 00 50 100 150 200

Footing(FT) Micropile(MP) MP footing(FT-MP)

Load, q (kN) Displacement, S (m)

Loose Sand Ground

0. 06 0. 05 0. 04 0. 03 0. 02 0. 01 0. 00 100 200 300 400

Load, q (kN) Displacement, S (m)

Dense Sand Ground

Vertical Loading Condition

FT+MPs FT+MPs

R= FT-MP FT+MPs

Network effect index (Confining Effect)

Vertical Loading Condition

20000 156

FT-PSMP

19000 123

FTMP Initial Coefficient

• f 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. 00 50 100 150 200

with prestress without prestress

Load, q (kN) Displacement, S (m)

Loose Sand Ground

0. 06 0. 05 0. 04 0. 03 0. 02 0. 01 0. 00 100 200 300 400 500

Load, q (kN) Displacement, 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. 00 10 20 30 40 50

Load, q (kN) Displacement, S (m)

Loose Sand Ground

MP(Micropile)

0. 06 0. 05 0. 04 0. 03 0. 02 0. 01 0. 00 10 20 30 40 50 60 70 80

MP(Micropile)

wi th pr estr ess wi thout pr estr ess

Load, q (kN) Displacement, S (m)

Dense Sand Ground

Horizontal Loading Condition

650 38

FT-PSMP

630 23

FTMP Initial Coefficient

• f subgrade reaction

Critical bearing capacity

820 67

FT-PSMP

760 31

FTMP

Loose sand Dense sand

(Effect of prestress)

Summary and future plan

The confining effects on the ground by the

micropiles were clearly observed both in the loading tests and FEM simulations

The 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 modified

The yielding of micropiles under the horizontal

loading on piles

The increase in shear modulus of ground due

to the confinement

3-D FEM simulation

network of micropiles confining effect

Thank you for your attention !

End of the Presentation