1. Masashi ITANI Takeshi OSHITA Seiichi ONODERA
IWM200３
Outline of the Execution Manual for Seismic Retrofitting of Existing Pile Foundations with High Capacity Micropiles
Masashi ITANI
Takeshi OSHITA
Seiichi ONODERA
Thank you, Chairman.
My name is Masashi Itani.
I belong to construction technology research team, PWRI.
I’ll talk about “outline of the execution manual for seismic retrofitting of existing pile foundations with High Capacity Micropiles.
Public Works Research Institute
Construction Technology Research Team.

2. Contents of the Executive Manual
This manual was compiled based on the Design Specifications for Highway Bridges in Japan. Also, the Execution Manual describes a construction method that closely resembles that for High Capacity Micropiles, or HMP.
It was created using the basic ground anchor varieties as a reference.
First, I'll explain the composition of the manual's table of contents. Here is the composition of the manual's table of contents:
The basic execution items are identical to the HMP execution methods in the United States. The items for quality control standards are based on the Japanese ground anchor standards.
I'll give a simple explanation of the content in the same order as the manual's table of contents.

3. Caputure 1 ： Gemeral Scope
This manual covers the execution of seismic retrofitting of existing pile foundations using high capacity micropiles.
The first chapter of general regulations indicates that this manual is applicable only when applying HMP to the seismic retrofitting of existing foundations.

4. Contents of the Executive Manual
The second chapter consists of general categories related to the execution.

5. Caputure 2 ： GENERAL ITEMS CONCERNING EXECUTION
Major Items Surveyed in Preparation for Execution
Category
Survey item
Working environment conditions
Limit on overhead space
Plane execution yard conditions
State of surrounding roads
Existing structures
Adjacent structures and underground structures
State of rivers etc.
Execution ground
Temporary equipment
Natural conditions
Surrounding environment conditions
State of surrounding region
State of nearby roads
Legal restrictions on construction work
Byproducts of construction
Ground conditions
Soil
Groundwater
Here, it primarily describes the categories that must be surveyed in advance when applying HMP to the seismic retrofitting of existing foundations.
The primary survey categories are as follows.

6. Preliminary surveys Limit on overhead space 4m
For the survey of the height of the overhead space, it is necessary when retrofitting existing foundations to consider the limits on overhead space, including overhead wires, the superstructure, and the bridge pilings.
The overhead space restrictions will have an effect on such factors as selecting the work machinery, the length of the rod used for the boring, the length of the material for each steel pipe used, and the number of couplings.
This will have a significant impact on the construction period and expenses.
Therefore, there will be a complete survey of the overhead space restrictions of the area surrounding the location where the HMP piles will be driven Also, the selection of the machinery for the execution and the materials will be studied.
In order to retrofit an existing pile foundation, the restriction on the overhead space imposed by overhead wires, the superstructure, the beam of the bridge pier etc.

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.
Next is the study of the conditions of the plane layout of the execution yard.
There often will be many restrictive conditions for securing the area around the existing foundation, as people and businesses are conducting a wide range of activities there.
Therefore, a study of the plane layout of the execution yard will require surveys of the site boundary location, the conditions of use and structures in the space below the bridge, and the area, location, and ground height differentials of the site that can be used as the execution yard.
It also will be necessary to fully examine the placement of the machinery for execution and the plant equipment, the yard topography, and the location of the transport road for the site.

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.
Sufficient surveys also must be conducted of the nearby structures.
These will include the structural design of existing structures (existing footings, bridge pilings, etc.), the adjoining structures near the location where the HMP piles will be driven, and the location and condition of underground structures.
Further, depending on the conditions of the nearby structures and the structures underground, a preliminary study will be required to determine if there will be any effect on the nearby structures themselves when the base of the surrounding foundation is dug and the HMPs are driven.
It also may be required to devise alternative work measures and observe the movement during work.

9. Contents of the Executive Manual
I will now provide an explanation of the execution method in Chapter 3.
This chapter describes the HMP execution method.
Basically, the execution method is the same as the HMP execution method used in the U.S.
The standard HMP execution process consists of boring, installing the core bars, mixing the grout, the initial injection, pressurized injection, reinsertion of HMP steel pipe, and treatment of the pile head.
As a rule, the execution for a single HMP will be a continuous process from the start of the boring to the reinsertion of the HMP steel pipe.
That is because halting the boring work will make it difficult to insert and extract the HMP steel pipe.
Also, halting the grout injection work is likely to have a harmful effect on the quality of the hardened grout.

10. Major machinery and equipment
Sample of Standard Execution Machinety and Equipment
An example of standard machinery and equipment is here, Primary Machinery and Equipment, as follows.

11. Contents 3 : EXECUTION METHOD
HMP Exection Process
I explain the contents of a manual according to the order of execution.
First, it is installation of a bowling machine.
The installing angle is set using a slant rule.

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

13. Boring Method Selection of Boring Method Accoding to Ground Category
down-the-hole hammer
Rotary percussion
Now, I will present an explanation of the boring method.
Considering past results, the hole boring method will be as a rule either the rotary percussion double pipe method or the down-the-hole hammer double pipe method.
Also, selecting the boring method based on the ground classification is shown here as a reference.

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

15. Boring
Boring shall be performed by an all-casing method to protect a borehole wall. At this time HMP steel pipes shall be used as the casing. If the boring is completed, the inside of the borehole shall be carefully washed to remove slime.
My next explanation is about boring
The boring is done using the all casing method to protect the borehole wall.
At that time, the HMP steel pipe is used as a casing.
When the boring is complete, slime processing is conducted by cleaning out the interior of the borehole as a precaution. In terms of design, HMPs are not expected to have superior bearing strength,
but this process is performed in consideration of the effect the slime will have on grout quality and the friction strength between the grout and the surrounding ground.
There are also concerns that the Bentonite ?mud will have an effect on the friction strength between the ground and the grout, so its use is avoided except in special circumstances.

16. Contents 3 : EXECUTION METHOD
HMP Exection Process
Withdrawing inner rod.
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
Mixing grout.

19. Grout injection Grout Mixture Sample 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
Grout composition is determined by trial mixing on site to satisfy the requirements for the standard design strength, and the workability for the feeding and injection. The standard design strength shall be at least 30 N/mm2. It is set at this level to ensure the designated workability during injection. The standard composition is as shown in this chart (For PPT?).
This composition is determined using as a reference the cement milk composition used for ground anchor execution in Japan. Also, the execution results for the ground anchor present no particular problems for the use of the chemical admixture, such as fly ash, superplasticizer, and retardant.

20. Contents 3 : EXECUTION METHOD
HMP Exection Process
grout
Initial injection

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

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

23. Contents 3 : EXECUTION METHOD
HMP Exection Process
Treatment of pile head
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.
To continue, I will explain pile head processing.
The joining methods for the pile head steel pipe and the footing are the bearing plate method and the shear method shown here.
Precautions during execution using the bearing plate method involve providing an inlet and an air vent in advance and focusing on the grout after tightening the pile head steel pipe, because the interior of the pile head steel pipe is a tightly sealed cavity.
Also, the emergence of a large gap in the concrete near the bearing surface will create stress and the formation of a broken surface unanticipated in the design.
It is possible that a situation will be created in which the required durability cannot be maintained, so the area around the bearing plate must be fully tightened to ensure that a harmful gap is not created.

25. Contents of the Executive Manual
Now, we'll move along to the quality control category.

26. CHAPTER 4 : EXECUTION MANAGEMENT
PROCESS : Boring
The quality control category and the standard quality values for the HMP are determined in the following manner.
As I explained previously, the managed values shown here conform to Japanese grout anchor standards.
The placement accuracy when installing the borehole machine is an eccentricity volume of less than 1/4 of the pile diameter, and a pile driving angle of less than 1/4. D
Eccentricity : D/4

27. CHAPTER 4 : EXECUTION MANAGEMENT
PROCESS : Boring
Also, the accuracy of the boring angle is less than +- 1 degree.
±１°

28. CHAPTER 4 : EXECUTION MANAGEMENT
PROCESS : Grout injection
　　This is established in conformity with the Japan Concrete Standard Specifications.
The quality control for the grout during execution is primarily for the overflow grout during pressurized injection.
Trials are conducted of the overflow grout to determine its specific gravity, the volume of chloride, the compression strength, and the bridging ratio.
The specific gravity should be within +-2% during mixing, and the chloride volume should be within 0.30 kg/m3.
If it is very difficult to acquire material with a low chloride volume, it is acceptable to use material with a chloride ion mass of less than 0.6 kg/m3.
This is established in conformity with the Japan Concrete Standard Specifications.
The compression strength of the grout should be greater than the standard design strength, and the bridging ratio should be less than 3% three hours later.

29. CHAPTER 4 : EXECUTION MANAGEMENT
PROCESS : Installation of reinfoecing material
The manner of finishing when the pile driving is completed is as follows.
The position of the pile head: mm.
±50mm

30. CHAPTER 4 : EXECUTION MANAGEMENT
PROCESS : Pile head treatment
±2.5°
The position of the pile core: within 1/4 of the pile diameter.
The pile driving angle: degrees.
These standard values are established as a range that should not cause a problem in terms of design. 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.
Next is an explanation of confirming the HMP's bearing strength.
The bearing strength is confirmed during HMP execution.
As a rule, this is done in one of two ways.
Either trial piles are executed, followed by the confirmation of HMP workability and conducting bearing trials on the pile, or the design bearing strength is confirmed with a bearing trial for the main pile.
These may be omitted, however, if there is a full understanding of the workability at the worksite and it is easy to estimate bearing strength using a soil quality survey.
The reason is that the HMP method is a relatively new in Japan, and there have been an insufficient number of results until now to evaluate its performance.
For the load bearing test, it is desirable to execute a trial pile, add a load with a secondary critical force, and then determine the behavior of the pile in the ground.
It also would be acceptable to confirm the design bearing strength using the main pile if it would be difficult to conduct a bearing test due to the work period, the execution period, and cost considerations.
In past HMP perpendicular load bearing trials, it was reported that in the relationship of the load and the displacement to primary critical force, there was no difference between push-in and pull-out.
Therefore, either push-in or pull-out is acceptable for the bearing direction.
The bearing test shall be conducted in accordance with Japanese Geotechnical Society standards.
The compulsory measurement categories include the load and displacement volume at the pile head.
It would be desirable to measure the pile body strain as necessary.
Also, it would be acceptable to seek the allowable bearing load in accordance with of the Design Manual using the results of the bearing test.
The number of trial piles will be determined considering the total number of piles to be driven, the scope of the work and other factors.
If there is a full understanding of the workability at the work site and it is easy to estimate the bearing load through soil quality surveys, however, it would be acceptable to omit the load bearing test to confirm the load bearing.
(2) The design bearing capacity is confirmed to perform a vertical loading test on an actual pile.

32. Outline of the Integrity test
Hand hammer
Acceleration senser
computer
pile
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. Principle of the Integrity test
Speed
depth
time
Pile length（L）
speed
Pile length (L)

34. Tese case Case1 3@1,500=4,500 pipe Grout lod 178 250 500 750 1,500 750
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. Ground test
1,500
4,500
7,500
支持層
This created a longer anchored portion than originally designed.

39. CONCLUSION Applicability for HMP quality control
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. My presentation is finish.