CAST-IN-PLACE REINFORCED CONCRETE EXPANSION BOTTOM PILE

PURPOSE:To enable smooth and effective transmission of the load of an upper structure to a support ground by a method wherein the length of a cast-in-place reinforced concrete pile the long term allowable support force of which is determined according to a relation formula is set to a value higher than a given length and the tip part of a pile shaft is expanded. CONSTITUTION:The length of a cast-in-place reinforced concrete expansion bottom pile is set to 5.5mm or more, and the size of the bottom of the tip thereof is increased to a value sharply higher than a shaft diameter (r) by an expansion part 2 formed at the periphery of the tip part. The height of the expansion part is regulated to a value 4.1 times or more as large as a shaft radius, the vertical height of an expansion inclination part to a value approximate 3 times as large as a shaft radius, and the radius of the expansion bottom to approximate 1.78 times as large as a shaft radius. The inclination angle of the sectional rapid change part of an expansion inclination part is limited to a range of 11 deg.26'-11 deg.30'. This constitution relieves the local stress of the sectional rapid change part and hardly generates a crack.