| 摘要 |
PROBLEM TO BE SOLVED: To provide an excavation tool capable of performing excavation while making a bore hole self-supported even in soft ground. SOLUTION: In this excavation tool, an expansion bit 3 is attached, in which an outer diameter from the center axis line O is enlarged by the rotation during excavation of the device 2 in a freely rotatable manner around a rotation axis line X eccentric from the center axis line O, a plurality of rows of projected stripe portions 25 extending in peripheral direction are formed in X direction of the rotation axis line X at the side face 21C facing the outer peripheral side of the tool during the enlargement of the diameter of the bit 3.
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