PURPOSE: To obtain a large bearing force at the front of a pile or the like by making the bottom of an excavated hole or the front end of a pile body constituting a cast-in concrete pile to be semi-spherical.
CONSTITUTION: The ground 6 is excavated with rotation by a downward arc shaped and semi-circular bit 8. Hereafter, a solidifying liquid for the bottom like cement milk 8 is poured into the excavated hole bottom of the pile hole 1. And the bit 8 is lifted and a steel rod frame 10 is settled in the pile hole 1. Then, concrete 11 is placed. In this way, the front end of the pile is formed semi-spherical and a high shearing rigidity of the bearing ground 7 can be obtained after excavating of the ground and the bearing ground 7 of the excavated hole bottom 3 can be prevented from loosening to get a large bearing force at the front.
YAMASHITA KIYOSHI
KAKURAI MASAAKI
TAKENAKA DOBOKU