| 摘要 |
PROBLEM TO BE SOLVED: To provide a widening excavation method capable of widening and forming a lower end of a concrete pile to a sufficient depth.SOLUTION: A widening excavation method includes: a first step of excavating an excavation hole of a diameter corresponding to a pile diameter of a concrete pile; and a second step of rotating a bucket 10 provided with a cylindrical bucket body of a diameter smaller than that of the excavation hole 30a, a bottom part 13 having first excavating claws for excavating below the bucket body and expansion blades 14 opening from a side face of the bucket body and having second excavating claws for excavating an outer peripheral side of the bucket body at its lower end to dig while widening the diameter of a front end of the excavation hole. The second step includes: a third sub-step of lowering the expansion blades 14 to the front end of the excavation hole while storing the expansion blades 14 in the bucket body; and a fourth sub-step of opening the expansion blades 14 and bringing second excavating claws and the first excavating claws of the bottom part 13 into contact with the front end of the excavation hole when the bucket body comes in contact with the front end of the excavation hole. |
