| 摘要 |
PROBLEM TO BE SOLVED: To completely prevent generation of puffiness in ground in a laying bedrock from starting of laying of an underdrainage pipe to completion of back filling, maintain accuracy of a gentle slope by an original laser optical system, and automatically and efficiently lay the underdrainage pipe. SOLUTION: A large sized dipping trencher or dipping plow is equipped. In that case, a box shaped pipe box 8 is connected behind the dipping trencher 1 or a dipping plow, a folding plate 3 in a V-shaped cross section is used as a bottom plate of the pipe box 8, and a weight 4 rotatively attached around a supporting shaft 5 is stored in a lower part of the pipe box 8.
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