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Horizontal Loading Tests on Model Foundations Retrofitted by Micropiles

Explore the effects of retrofitting existing foundations with micropiles through horizontal loading tests. Results and simulation analyses are used to study the retrofitting design method. Correction factors for both single piles and group piles are analyzed to understand group effects.

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Horizontal Loading Tests on Model Foundations Retrofitted by Micropiles

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  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

  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 7 Case 6

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

  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 =aｋbｋkH pHU =aｐbｐpU 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 : 1

  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 φy ０ (1/m) Curvature

  33. 40 0 20 60 80 100 120 140 40 80 100 120 0 20 60 0 20 40 60 80 100 Curve of Load and Displacement

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

  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.

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