Masashi ITANI Takeshi OSHITA Seiichi ONODERA

1. Outline of the Execution Manual for Seismic Retrofitting of Existing Pile Foundations with High Capacity Micropiles Masashi ITANI Takeshi OSHITA Seiichi ONODERA IWM200３ Public Works Research Institute Construction Technology Research Team.

2. Contents of the Executive Manual

3. Caputure 1 ：Gemeral • This manual covers the execution of seismic retrofitting of existing pile foundations using high capacity micropiles. Scope

4. Contents of the Executive Manual

5. Caputure 2 ：GENERAL ITEMS CONCERNING EXECUTION Major Items Surveyed in Preparation for Execution

6. Preliminary surveys Limit on overhead space 4m In order to retrofit an existing pile foundation, the restriction onthe overhead spaceimposed byoverhead wires,the superstructure,the beam of the bridge pieretc.

7. Preliminary surveys Survey of the execution yard condition The plane layout of the execution yard must be studied by surveying the site boundaries, structures and uses under girders, areas and locations that can be used as the working yard, level differences of the ground etc.

8. Preliminary surveys Survey of adjacent and underground structure Structural specifications of existing structures (existing footings, bridge piers etc.), structures adjacent to the site where HMP is installed, and the location and state of underground structures must be thoroughly surveyed.

9. Contents of the Executive Manual

10. Major machinery and equipment Sample of Standard Execution Machinety and Equipment

11. Contents 3 : EXECUTION METHOD HMP Exection Process The installing angle is set using a slant rule.

12. Contents 3 : EXECUTION METHOD HMP Exection Process Boring using 1.5m short HMP steel pipes (as standard) as a casing.

13. Boring Method Selection of Boring Method Accoding to Ground Category Rotary percussion down-the-hole hammer

14. Water or Air Contents 3 : EXECUTION METHOD HMP Exection Process The inside of the borehole is washed with pure water or air.

15. Boring Boring shall be performed byan all-casing methodto protect a borehole wall. At this time HMP steel pipes shall be used asthe casing. If the boring is completed, the inside of the borehole shall becarefully washed to remove slime.

16. Contents 3 : EXECUTION METHOD HMP Exection Process The injection hose and core bars are inserted into the borehole together.

17. Contents 3 : EXECUTION METHOD HMP Exection Process The injection hose and core bars are inserted into the borehole togethor.

18. Contents 3 : EXECUTION METHOD HMP Exection Process

19. Grout injection Grout Mixture The grout mixture must be set so that it satisfies the design strength of 30N/mm2 or more, and the stipulated workability during pumping and injection. Sample Grout Mixture

20. grout Contents 3 : EXECUTION METHOD HMP Exection Process

21. Contents 3 : EXECUTION METHOD HMP Exection Process Pressure injection is perfomed to the stipulated depth each time HMP steel pipes are without.

22. Contents 3 : EXECUTION METHOD HMP Exection Process HMP steel pipes are reinserted to the stipulated depth.

23. Contents 3 : EXECUTION METHOD HMP Exection Process Treatment of pile head.

24. Treatment of the pile head Pile head steel pipes and a footing are connected by a bearing plate method or shear ring method.

25. Contents of the Executive Manual

26. CHAPTER 4 :EXECUTION MANAGEMENT PROCESS : Boring D Eccentricity : D/4

27. CHAPTER 4 :EXECUTION MANAGEMENT PROCESS : Boring ±１°

28. CHAPTER 4 :EXECUTION MANAGEMENT PROCESS : Grout injection This is established in conformity with the Japan Concrete Standard Specifications.

29. CHAPTER 4 :EXECUTION MANAGEMENT PROCESS : Installation of reinfoecing material ±50mm

30. CHAPTER 4 :EXECUTION MANAGEMENT PROCESS : Pile head treatment ±2.5° D Eccentricity : D/4

31. Confirming the bearing capacity of HMP In principle, one of the following shall be performed to confirm the bearing capacity of HMP (1) A test pile is executed to confirm the execution properties and to perform a vertical loading test. (2) The design bearing capacity is confirmed to perform a vertical loading test on an actual pile.

32. Hand hammer Acceleration senser pile computer Outline of the Integrity test • It is performed by creating a low level strain by lightly striking the pile head with a hand held hammer and measuring the response at that time with an accelerometer.

33. speed Speed time time Pile length（L） time time Pile length (L) depth depth Principle of the Integrity test

34. Tese case Case1 3@1,500=4,500 pipe Grout lod 178 250 500 750 1,500 750 750 750 2,250 3,000 6,750

35. Tese case Case2 45° 3m 1m

36. result Case1 • The reflection from the end of the steel pipe and the end of the pile is clearly observed. speed end of the steel pile End of the grout Pile head length

37. result Case２ speed end of the steel pile End of the grout Pile head Length(m)

38. 4,500 4,500 4,500 7,500 7,500 7,500 支持層 支持層 1,500 1,500 1,500 1,500 1,500 1,500 1,500 1,500 1,500 1,500 1,500 1,500 Ground test This created a longer anchored portion than originally designed.

39. CONCLUSION • The effect on the ground can be reduced by processing the amplitude of the measured waveform, even for HMPs with their complex structure. • The reflecting wave form the grout expansion portion, the end of the steel pipe, and the pile can definitely be measured to a certent. Applicability for HMP quality control ・We believe an effective method would be to compare the survey results for all the HMPs and to select those piles that can be expected to perform poorly based on a relative evaluation.

40. END Thank you for your attention.