| 摘要 |
PROBLEM TO BE SOLVED: To make extension piles bear a sufficient axial force. SOLUTION: In this extension pile constructing method, a PC steel bar 2 as tension materials is inserted inside a hollow precast pipe 1, the lower end of the PC steel bar 2 is fixed to a pile bottom 3, and the upper end of the PC steel bar 2 is inserted into a loading plate 4 provided at pipe heads and spirally engaged with a nut 5 for fixation, and the nut 5 for fixation is screwed to introduce a predetermined prestress force to the hollow precast pipe 1. The prestress-force-introduced hollow precast pipes 1 as extension piles are driven into the ground around a previously provided footing 7. Then hollow pipes 11 for work are raised on the loading plate 4 of the hollow precast piles 1 so as to surround the nuts 5 for fixation. An extension footing 13 is constructed to be integrated with the previously provided footing 7. After the manifestation of the strength of the extension footing 13, the nuts 5 are loosened through the use of a space 12 for work inside the hollow pipes 11 of work to unload the prestress force introduced to the hollow precast pipes 1.
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