| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that such a phenomenon is particularly possibly caused that the granulation of soil does not sufficiently advance, or coarse gravel exists, though there are extremely many cases that the inner wall of a drill pipe and a conveyor screw are relatively early and easily worn by this delay, since the fact that the progress of excavation becomes relatively slow in a specific state is known in twin head type excavation. SOLUTION: This method excavates a boring hole in the soil, and carries out an exposed soil substance by the conveyor screw in a drill pipe, by loosening the substance by at least one main edge provided in front in the axial direction of the conveyor screw, by penetrating into the soil, while rotating the drill pipe and the conveyor screw arranged in the drill pipe. The main edge is arranged on the drill pipe following this operation, and is rotated together with the drill pipe. This device can also be used in this method for excavating the boring hole in the soil. COPYRIGHT: (C)2008,JPO&INPIT
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