Quality control of High Capacity Micropiles (Seismic Retrofit Construction of a service water pond at KAMEIDO in TOKYO) Masao Sagara (Fujita Corporation) Junya Hayashi (Waterworks, Tokyo Metropolitan Government)

Contents ① Background ② Purpose ③ Outline of construction and Quality control ④ Result and consideration ⑤ Conclusion

① Background (Outline of Kamaido service water pond)

Kamaido service water pond ground plan a cross section Built in 1970 height ; 7.7m Width; 104m×104m Volume of water kept in store; 60,000m 3 104m 7.7m

Kamaido service water pond In the upper part, there are a baseball ground and tennis courts.

Kamaido service water pond Existing piles 35 ～ 48m φ600mm The number of existing piles are 1696.

The Hyogoken-nanbu earthquake happened in Specifications for Water installations was revised in Kamaido service water pond did not satisfy Specifications for Water installations. By the way

Kamaido service water pond HMP Existing piles 35 ～ 48m φ600mm 38 ～ 48m φ178mm

② Purpose

Purpose The number of existing piles are It is worried that the existing piles comes in contact with HMP when HMP is constructed. Do to examine whether HMP comes in contact with the existing paling.

③ Outline of construction and Quality control

Ground plan It has divided into nine blocks by expanded joint. 8 HMP are constructed by a block. The construction of 72 of 9×8 in all is scheduled. Six was constructed in this time. Expanded Joint

Ground plan(Expanding figure) HMP are batter piles. Existing piles HMP

Construction image (A cross section) The ground is a very soft ground up to about 35-43m. The ground becomes hard at deeper position than it. HMP is constructed between the existing piles. N value Existing piles HMP

Construction (batter pile) Plastic Bit

Construction process chart

Quality control ① Investigation of torque ② Angle measurement ③ Measurement with inclination meter

Investigation of torque

Investigation result of torque The rotating torque showed the tendency to increase if reaching the bearing ground in the drilling. Torque(Mpa) depth(m )

Angle measurement

Measurement with inclination meter

Result of Measurement with inclination meter

The angle of the paling of all the palings was ±1°. This value was more excellent than construction control value ±2.5° on general paling head

Conclusion It was thought that the adoption of a plastic bit was good for the anxiety about the contact of the existing paling and HMP. It was confirmed that the construction accuracy of batter pile of HMP was excellent.The accumulation of further data will be hoped for in the future. It was thought that the measurement of the rotating torque of the drilling machine was one of effective construction control techniques as the judgment material which confirmed the attainment to the supporting soil.