| 摘要 |
PURPOSE:To form a drain canal with lesser area loss by a method in which a bullet borer is integrally provided to the back of a rotary blade of an inversed trapezoidal form for excavating an open conduit, and a bullet culvert is constructed in the portion deprived of crushed soil at the same time in such a way as to allow the permeation of drain into cracks continuously. CONSTITUTION:A rotary blade 2 is provided in the front of a frame 1 to be dragged by the three-point supporter (not illustrated) of a tractor. The left- handed side 8 of a drain canal 6 is excavated by a cutter 11, the right-handed side 9 is excavated by a cutter 12, the bottom 10 is excavated by a cutter 13, and the shape of the canal 6 is rectified by a rectifying board 14. Also, a vertically movable and back and forth-inclinable bullet borer 15 is provided at the center of the board 14. Crushed soil 16 is rejected by the blade 2 and then a bullet culvert 17 is formed. In this case, cracks (not illustrated) are developed in the shearing portion of the culvert 17 due to early drying effect, and thereby the vertical permeation of drain is continued and rapid and effective drain treatment is thus attained. |
