| 摘要 |
PURPOSE:To enable turning propulsion from a specified position easily by installing an excavating section under the state, in which only revolution in the periphery of an axial core is permitted, to a propulsion head body and mounting a piston to the propulsion head body and said excavating section in a reciprocative manner. CONSTITUTION:A head 1 for propulsion is formed of a small-diameter head body 1A, an excavating section 1B and an operating device 7, and a water injection nozzle 8 is set up to the excavating section 1B. When the head 1 for propulsion is rectilinearly propelled, the excavating section 1B is propelled turned in order shown in (a), (b) and (c) respectively to the head body 1A. When the head is rotated, a pressure receiving surface F receives earth pressure and the propulsive direction of the head 1 for propulsion is directed toward the side reverse to the pressure receiving surface F when the water injection nozzle 8 is directed toward the side to be turned while the pressure receiving surface F is directed toward the side reverse to the side to be turned and the head is propelled. Since soil texture on the turning side is weakened by the water injection nozzle 8 at that time, resistance received from soil is reduced, thus rotating the head 1 for propulsion in the small radius of curvature. |
