| 摘要 |
PROBLEM TO BE SOLVED: To provide a center drilling excavator for improving working efficiency, by installing the center drilling excavator in an optional position in an excavating casing and executing excavation work in the position, enabling the executing of a bottom expansion in the hard ground, the bottom expansion of a large diameter and rock excavation, and also discharging excavated sediment outside a vertical hole together with injected water for preventing collapse of the vertical hole.SOLUTION: A center drilling excavator 1 is installed in an excavating casing 7 used for an all-casing method, and is composed of: a driving device 2 which is fixed in a detachable manner in the excavating casing 7 and includes a cylindrical driving shaft 9 provided in a rotatable and liftable manner and having a vertical attitude; a bottom expansion reverse head 3 having a hollow rod 14 connected to a lower end part of the driving shaft 9 and forming a sediment suction port 14a on the tip, and diametrically expanding a bottom part of a vertical hole not surrounded by the excavating casing 7; a sand pump 5 connected via a swivel joint 4 to an upper end part of the driving shaft 9; and a discharge hose 6 connected to the sand pump 5. |
