| 摘要 |
PROBLEM TO BE SOLVED: To improve the accuracy of the execution of works by inserting a curved propulsive body into a linear hole drilled by a rectilinear propulsive body, in which a maximum diameter is specified, and drilling a curved hole after the linear hole. SOLUTION: A front end is formed in a tapered shape in the rectilinear propulsive head 24A of a rectilinear propulsive body 3A while a maximum diameter is set in 1.3 times or more as large as the diameter of a rectilinear propulsive pipe 25A, and an inclined turning pressure-receiving surface 24a is formed at a front end in the curved propulsive head 24B of a curved propulsive body 3B, and the pipe 25A and a curved propulsive pipe 25B are extended in a concentric series shape at the time of soil propulsion. A linear hole in required length is bored by the propulsive body 3A at the time of the execution of works, the pipe 25A and the propulsive body 3A are extracted and the propulsive body 3B is inserted up to the front end of the linear hole. Since the diameter of the head 24B is made smaller than the head 24A at that time, resistance at the time of insertion is lowered. Upward earth pressure is applied to the pressure-receiving surface 24a by the front end of the linear hole, and the propulsive body 3B is propelled upwards and made to reach an aimed ground-surface place. Accordingly, the linear hole can be drilled easily with high accuracy, and can be made to reach the arrival place of a ground surface accurately. |
