| 摘要 |
PROBLEM TO BE SOLVED: To enable the excavation of a small diameter as much as possible at the time of curvilinear excavation and to enable excavation associated with percussion. SOLUTION: Through the use of a bent external pipe 11 bent at a predetermined curvature and a linear internal pipe 13 inserted into the bent external pipe 11 and provided with an excavating bit 12 at the tip part, the excavating bit 12 of the internal pipe 13 is protruded from the tip of the external pipe 11, and a rotating force and a propulsive force are provided for the base part of the internal pipe 13 to rotate and propel the excavating bit 12. In addition, by propelling the external pipe 11 without rotating it, the ground is curvilinearly excavated. |
