1. Horizontal Loading Tests on Model Foundations
Retrofitted by Micropiles
Masahiro NISHITANI
Jiro FUKUI
Takeshi UMEBARA
　　IAI, PWRI
　　Structures Research Group
　　Foundation Engineering Team

2. Retrofitting of Existing Foundation by Micropiles
Limited Headroom
Widening of Footing
Existing Pile
Micropile
Bearing Layer

3. Presentation Outline
Outline of horizontal loading tests on group piles
Results of horizontal loading tests
Results of simulation analyses for the loading tests
Summaries

4. Presentation Outline
Outline of horizontal loading tests on group piles
Results of horizontal loading tests
Results of simulation analyses for the loading tests
Summaries

5. To Clarify the Effects of Group Piles….
Existing Footing
Existing Pile
Micropile
Plane of Existing Foundation with Micropiles
→ Horizontal Loading Tests on Model Foundations

6. Cases of Horizontal Loading Tests

7. Case 1
Case 2

8. Case 3
ケース３は、既設４本杭の補強前の基本ケースです。

9. Cases of Horizontal Loading Tests

10. Models of Case 4 to Case 7 Rear Front Micropile Existing Pile
Loading Direction

11. Case 4
Case 5

12. Case 6
Case 7

13. Specifications of Model Piles

14. Loading Test for Case 3
Jack
Steel Bar
Footing

15. Presentation Outline
Outline of horizontal loading tests on group piles
Results of horizontal loading tests
Results of simulation analyses for the loading tests
Summaries

16. Curve of Load and Displacement

17. Bending Moment on Existing Piles in Case 3 and Case 4

18. Bending Moment on Existing Piles in Case 4 and Case 6

19. Bending Moment on Micropiles in Case 4 and Case 6

20. Shearing Force on Existing Piles in Case 3 and Case 4

21. Shearing Force on Existing Piles in Case 4 and Case 6

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

23. Axial Force on Existing Piles in Case 4 and Case 6

24. Curve of Horizontal Ground Reaction and Displacement
1.5
2.0
1.0
0.5
0.0

25. Presentation Outline
Outline of horizontal loading tests on group piles
Results of horizontal loading tests
Results of simulation analyses for the loading tests
Summaries

26. To Study the Design Method of
Group Piles with Different Diameter Piles….
→ Simulation Analyses for Loading Tests by
Ductility Design Method
Non-Linear Model
・Ground Properties
・Flexural Rigidity of Piles

27. Model of Transverse Resistance of Pile
(N/m2)
Upper Limit of Ground Reaction
Ground Reaction
ＰHU
Ｔan－１ｋHE ０
Displacement
(m)

28. Transverse Resistance Characteristics of Pile
kHE = aｋbｋ kH
pHU = aｐbｐ pU
　aｋ, aｐ: Correction Factors of a Single Pile
　bｋ, bｐ: Correction Factors of Group Piles
To consider the group effects…
　aｋ bｋ = 1
　 aｐ (Cray Ground) = 1.0
　 aｐbｐ (Sandy Ground) = S/D (≦3)
To consider the group effects of trailing piles…

29. Loading Direction
Rear
Front
Trailing Piles
Front Pile
pHU ½ :

30. Simulation Procedure
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

31. New Correction Factors on Analyses

32. Model of Flexural Rigidity of Steel Pile
(Nm)
Bending Moment
Fully Plastic Moment Mp Y My
Y: Yield State ０ φy
Curvature
(1/m)

33. Curve of Load and Displacement
120
140
100 80 60 20 40

34. Bending Moment on Existing Piles in Case 3 and Case 4

35. Bending Moment on Micropiles in Case 4

36. Curve of Horizontal Ground Reaction and Displacement
Case 3

37. Curve of Horizontal Ground Reaction and Displacement
Case 4

38. 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.