| 摘要 |
PROBLEM TO BE SOLVED: To allow the drilling bucket of a hydraulic shovel to vertically drill one side without being slid down to an existing drill hole when drilling one side of the existing drill hole of a soft rock layer. SOLUTION: A plurality of bottom bits G1, G2 including at least the bottom bits G2 at both ends are protruded from the bottom plate tip 50 of a bucket B, and side bits K1 having taper faces 12 on at least a pair of inner faces are protruded from both side plates nearly in parallel near the bottom bits G2 at both ends on the side view. When one side wall face of an existing drill hole H is drilled with the bucket B, the side bits K1 cooperating with the bottom bits G2 generate outward bias stress while cutting a soft rock layer, and the bucket B is prevented from being slid down to the existing drill hole H side by the bias stress.
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