Horizontal Loading Tests on Model Foundations Retrofitted by Micropiles

Horizontal Loading TestsHorizontal Loading Testson Model Foundationson Model Foundations

Retrofitted by MicropilesRetrofitted by Micropiles

Masahiro NISHITANIJiro FUKUITakeshi UMEBARA

　　 IAI, PWRI 　　 Structures Research Group 　　 Foundation Engineering Team

Retrofitting of Existing Foundation by Micropiles

Limited Headroom

Widening of Footing

Existing Pile

Micropile

Bearing Layer

Presentation Outline

• Outline of horizontal loading tests on group piles

• Results of horizontal loading tests

• Results of simulation analyses for the loading tests

• Summaries

To Clarify the Effects of Group Piles….

→ Horizontal Loading Tests on Model Foundations

Plane of Existing Foundation with Micropiles

Micropile

Existing PileExisting Footing

Case Number of Piles

Spacing between ExistingPiles Center and

Micropiles Center

（mm）

Inclination Angle ofMicropiles （°）

1 Single Existing Pile －－

2 Single Micropile －－

3 4 Existing Piles －－

4 4 Existing Piles and 6 Micropiles 200 0




Cases of Horizontal Loading Tests

Case 1 Case 2

Case 3

Case Number of Piles

Spacing between ExistingPiles Center and

Micropiles Center

（mm）

Inclination Angle ofMicropiles （°）

1 Single Existing Pile －－

2 Single Micropile －－

3 4 Existing Piles －－





Cases of Horizontal Loading Tests

Models of Case 4 to Case 7

Existing Pile Micropile

Loading Direction

FrontRear

Case 4

Case 5

Case 6 Case 7

Diameter（mm）

Thickness（mm）

Sectional Area(cm2)

Moment of Inertia（cm4）

Existing Pile 114.3 3.5 12.18 187.0

Micropile 34.0 2.3 2.291 2.89

Specifications of Model Piles

Loading Test for Case 3

FootingSteel Bar

Jack





• Summaries

0

30

60

90

120

150

180

210

0 20 40 60 80 100Displacement of Footing mm（）

Load

kN（

）

Case1Case2Case3Case4Case5Case6Case7

Curve of Load and Displacement

-390

-330

-270

-210

-150

-90

-30

30-10 -5 0 5 10

Bending Moment kN m（･）

Gro

und

Leve

l cm

（）

Case3Front PileCase3Rear PileCase4Front PileCase4Rear Pile

Bending Moment on Existing Piles in Case 3 and Case 4

-390

-330

-270

-210

-150

-90

-30

30-10 -5 0 5 10


Gro

und

Leve

l cm

（）



-390

-330

-270

-210

-150

-90

-30

30-0.6 -0.4 -0.2 0.0 0.2


Gro

und

Leve

l cm

（）


Bending Moment on Micropiles in Case 4 and Case 6

- 390

- 330

- 270

- 210

- 150

- 90

- 30

30- 30 - 20 - 10 0 10

Shearing Force kN（）

Gro

un

d L

evel

cm

（）


Shearing Force on Existing Piles in Case 3 and Case 4

- 390

- 330

- 270

- 210

- 150

- 90

- 30

30- 30 - 20 - 10 0 10

Shearing Force kN（）

Gro

un

d L

evel

cm（

）


Shearing Force on Existing Piles in Case 4 and Case 6

- 390

-330

-270

-210

-150

-90

-30

30-60 -30 0 30 60 90

Axial Force kN（）

Gro

und L

evel

cm（

）

Case3 Front PileCase3 Rear PileCase4 Front PileCase4 Rear PileCase6 Front PileCase6 Rear Pile

Axial Force on Existing Piles in Case 3, Case 4 and Case 6

-390

-330

-270

-210

-150

-90

-30

30-20 -10 0 10 20

Axial Force kN（）

Gro

und

Leve

l cm

（）


Axial Force on Existing Piles in Case 4 and Case 6

1.5 2.01.00.50.0

1.0 1.50.50.0

Curve of Horizontal Ground Reaction and Displacement

400

300

200

100

00.0 0.5 1.0 1.5 2.0 2.5

Displacement of Pile (cm)

Hori

zonta

l G

round R

eact

ion (

KN

/m2 )

Case3 (G.L.-0.27m)Case3 (G.L.-0.57m)Case3 (G.L.-0.87m)Case4 (G.L.-0.27m)Case4 (G.L.-0.57m)Case4 (G.L.-0.87m)





• Summaries

To Study the Design Method of Group Piles with Different Diameter Piles….

→ Simulation Analyses for Loading Tests by Ductility Design Method

Ｐ

10

02

00

30

0

20

03

00

20

02

50

35

02

00

20

02

00

20

02

00

20

02

00

20

02

00

20

02

00

20

02

00

3,9

00

50

02

00

20

02

00

20

02

00

20

02

00

20

02

00

20

02

00

20

02

00

20

02

00

40

0

4,4

00Non-Linear Model

・ Ground Properties・ Flexural Rigidity of Piles

Model of Transverse Resistance of Pile

Upper Limit of Ground Reaction

Displacement

Gro

und

Rea

ctio

n

０

Ｐ HU

Ｔ an －１ｋ HE

(m)

(N/m

2 )

kHE = a ｋ b ｋ kH

pHU = a ｐ b ｐ pU　

　 a ｋ , a ｐ : Correction Factors of a Single Pile

　 b ｋ , b ｐ : Correction Factors of Group Piles

To consider the group effects…

　 a ｋ b ｋ = 1

　 a ｐ (Cray Ground) = 1.0

　 a ｐ b ｐ (Sandy Ground) = S/D ( 3)≦

To consider the group effects of trailing piles…

Transverse Resistance Characteristics of Pile

Loading Direction

Trailing Piles

FrontRear

Front Pile

pHU ½ : 1

1) Study new correction factors for a single pile, fitting with Case 1 test results

2) Study new correction factors for group piles, fitting with Case 3 test results 3) Analyze Case 4 to Case 6, using new correction factors

Simulation Procedure

ak bk ap ap・bp ak bk ap ap・bp

1, 2 1.5 － 3.0 －3.0

（×2）－

6.0（×2）

－

3 1.5 2/3 － *13.0

（×2）4/3

（×2）－ *2

4, 5, 6 1.5 2/3 － *13.0

（×2）4/3

（×2）－ *2

*1: S/D in Transvers Direction of Loading (Less Than and Equal 3)

*2: S/D in Transvers Direction of Loading (without Upper Limit)

CaseDuctility Design Method New Correction Factors

New Correction Factors on Analyses

Model of Flexural Rigidity of Steel Pile

Curvature

Ben

ding

M

omen

t

０

Mp

MyY

Y: Yield State

(Nm

)

(1/m)φy

Fully Plastic Moment

120 1401008060200 40

1201008060200 40

1008060200 40

0

30

60

90

120

150

180

210

0 20 40 60 80 100 120 140 160

Displacement of Footing mm（）

Load

kN

（）

Case3 TestCase3 AnalysisCase4 TestCase4 AnalysisCase5 TestCase5 AnalysisCase6 TestCase6 Analysis

Curve of Load and Displacement

-390

-330

-270

-210

-150

-90

-30

30-15 -10 -5 0 5 10

Bending Moment kN m（･）G

round

Leve

l (cm

)

Test Result on Front Pile

Test Result on Rear Pile

Analysis Resulton Front Pile

Analysis Resulton Rear Pile

-390

-330

-270

-210

-150

-90

-30

30-15 -10 -5 0 5 10


Gro

und

Leve

l (cm

)Test Resulton Front PileTest Resulton Rear PileAnalysisResult


Case 3 Case 4

-390

-330

-270

-210

-150

-90

-30

30-1.0 -0.5 0.0 0.5


Gro

und

Leve

l (cm

)

Test Result on Front PileTest Result on Rear Pile

Analysis Resulton Front PileAnalysis Resulton Rear Pile

Bending Moment on Micropiles in Case 4

Depth G.L.-0.57m；

400

350

300

250

200

150

100

50

00.0 0.5 1.0 1.5 2.0 2.5

Displacement of Pile cm（）

Hori

zonta

l Gro

und

React

ion

kN/m

（2 ）Test Result on Front PileTest Result on Rear PileModel on Front PileUsed in AnalysisModel on Rear PileUsed in Analysis


Case 3

Depth G.L.-0.57m；

300

250

200

150

100

50

00.0 0.5 1.0 1.5

Displacement of Pile cm（）

Hori

zonta

l Gro

und

React

ion

kN/m

（2 ）Test Resulton Front Pile Test Resulton Rear PileModel Usedin Analysis


Case 4

Summaries

• Results of horizontal loading tests → Existing foundations with micropiles have a

large retrofitting effects.

→ Spacing has little effect on retrofitting.

→ Retrofitting effects are counted by installing

micropiles incliningly.

• Results of simulation analyses → It is possible to use the ductility design method

to perform retrofitting design.

Horizontal Loading Tests on Model Foundations Retrofitted by Micropiles

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Transcript of Horizontal Loading Tests on Model Foundations Retrofitted by Micropiles