| 摘要 |
PROBLEM TO BE SOLVED: To increase tension resistance of an underground anchor. SOLUTION: The underground anchor is formed of spiral excavating blades arranged integrally intermittently at the top side of a shaft rod in the longitudinal direction thereof at predetermined intervals. The spiral excavating blades have an auxiliary blade which rotates on the shaft rod side when the shaft rod rotates around its axis in one direction and rotates in the direction of separating from the shaft rod side when the shaft rod rotates in the other direction. COPYRIGHT: (C)2006,JPO&NCIPI
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