| 摘要 |
PROBLEM TO BE SOLVED: To take in sediment easily in casing pipe in the excavation of a relatively large-diameter well. SOLUTION: A plurality of wings 30 are provided in a rotary casing pipe 2, at the lower plane of the wings, provided are a plurality of sediment guide wings 31b, 31c, 31d extending in a circular arc shape radial-outwardly in turning direction across the wing 30, and excavated sediment is sequentially guided radial-inwardly and taken in the casing pipe 2.
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