Outline of the Execution Manual for Seismic Retrofitting of Existing Pile Foundations with High Capacity Micropiles Masashi ITANI Takeshi OSHITA Seiichi ONODERA IWM200 ３ Public Works Research Institute Construction Technology Research Team.

Contents of the Executive Manual

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

Contents of the Executive Manual

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

Preliminary surveys §Limit on overhead space § 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. 4m

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.

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.

Contents of the Executive Manual

Major machinery and equipment §Sample of Standard Execution Machinety and Equipment

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

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

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

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

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.

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

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

Contents 3 : EXECUTION METHOD §HMP Exection Process

Grout injection § The grout mixture must be set so that it satisfies the design strength of 30N/mm 2 or more, and the stipulated workability during pumping and injection. §Grout Mixture §Sample Grout Mixture

Contents 3 : EXECUTION METHOD §HMP Exection Process grout

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

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

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

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

Contents of the Executive Manual

CHAPTER 4 : EXECUTION MANAGEMENT §PROCESS : Boring Eccentricity : D/4 D

CHAPTER 4 : EXECUTION MANAGEMENT §PROCESS : Boring ±１°±１°±１°±１°

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

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

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

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.

§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. Hand hammer Acceleration senser computer pile Outline of the Integrity test

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

3, , pipe lod Grout ,500 6, Case1 Tese case

1m 3m 45° Case2 Tese case

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

Case ２ result Length(m) speed Pile head end of the steel pile End of the grout

This created a longer anchored portion than originally designed. Ground test

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.

Thank you for your attention. END