Nisshin Steel Co., Ltd.

Takeyuki Yoshida

Takefumi Nakako

Toshiharu Kittaka

Masahiro Nakata

Kenji Ooshima

Shigeo Matsubara

Tatsurou Iwasaki

Hiromichi Shiroma

Tetsuo Itou

Hiroyuki Tanase

Hiroki Kanazawa

A sleevefor introduction of a pressurized fluid, which is attached to a rockbolt main body, comprises a cylindrical projecting partof a large diameter and a bearing-plate-holding partof a diameter smaller than an aperture of a bearing plate. The projecting partand the bearing-plate-holding partpreferably has the same inner diameter. When the rockbolt main bodyis embedded in a bedrock or ground, the bearing platelocates on an edge of a rockbolt-setting hole of the bedrock or ground, and the bearing-plate-holding partextends through the bearing plateinto the rockbolt-setting hole. Since the projecting partand the bearing plateare disposed on a sprayed concrete layer, a projection height of the rockbolt is remarkably decreased. Consequently, lining concreteis applied onto the sprayed concrete layer with ease, and the bedrock or ground is reinforced with high reliability.

Rockbolts made of steel pipes

A high-strength steel pipe rockbolt has an expansive rockbolt main body prepared by processing a high-strength steel sheet of 1.8-2.3 mm in thickness with a tensile strength of 490-640 N/mmand an elongation of 20% or more into a welded pipe and roll-forming the welded pipe into a shaped pipe having one or more concavities extending along an axial direction. Use of the high-strength steel sheet ensures sufficient strength of the shaped pipe regardless of a decrease in thickness. The thin welded pipe is also advantageous in resistance to cracking caused by accumulation of strains introduced during roll-forming, swaging both ends of the welded pipe and hydraulic expansion. Moreover, expansive deformation of the shaped pipe is initiated by injection of a pressurized fluid at a low pressure, so that the expansive deformation is completed in a short time period with an improved working efficiency.

Rockbolt of high strength steel pipe and method of manufacturing the same

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Hyogo, Japan

Takeyuki Yoshida