| 摘要 |
PROBLEM TO BE SOLVED: To eliminate rupture of an element tube in diameter-reduction processing and rupture of a steel pipe by residual stress of diameter-reduction processing, by reducing driving resistance of a screw part, by economically securing required strength for the screw part.SOLUTION: A natural ground reinforcing steel pipe 1 is constituted of a first pipe body 2 for continuously providing a main body 21 and a female screw part 22 for forming a female screw 221 on an inner peripheral surface and having the substantially same outer diameter in the axial direction and a second pipe body 3 for continuously providing a base part 31 having an outer diameter of the substantially same as the main body 21 and a thickness thicker than the main body 21 and a male screw part 32 formed in an outer diameter smaller than the base part 31 and forming a male screw part 321 on an outer peripheral surface and being in a shorter size than the first pipe part 2, and the female screw part 22 and the male screw part 32 have respectively a required thickness of becoming required strength for natural ground driving in a screw-connection state, and the edge on the base part 31 side of the second pipe body 3 is frictionally integrated in pressure contact with the edge on the main body 21 side of the first pipe body 2, and a taper part 33 of gradually diametrically reducing an inner diameter toward the male screw part 32 side from the substantially inner end of the edge on the main body 21 side of the first pipe body 2, is formed on an inner surface of a peripheral wall of the second pipe body 3.SELECTED DRAWING: Figure 2 |
