| 摘要 |
An under-reaming pile bore excavator by which a straight pile bore is first excavated vertically to a given depth by rotating the main drill bits and the under-reamed bore is next excavated downward and outward into a given shape by rotating the slidable wing bits, allowing a relatively larger diameter ratio of the under-reamed pile bore to the straight pile bore. The under reamed pile bore excavator of the present invention comprises a plurality of guide rails disposed so as to cross the axis of the drill pipe, and a plurality of slidable wing bits mounted on the guide rails which excavate the under-reamed bore, in addition to the conventional main drill bits which can excavate the straight pile bore.
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