Rockbolts made of steel pipes

A sleeve for introduction of a pressurized fluid, which is attached to a rockbolt main body , comprises a cylindrical projecting part of a large diameter and a bearing-plate-holding part of a diameter smaller than an aperture of a bearing plate . The projecting part and the bearing-plate-holding part preferably has the same inner diameter. When the rockbolt main body is embedded in a bedrock or ground, the bearing plate locates on an edge of a rockbolt-setting hole of the bedrock or ground, and the bearing-plate-holding part extends through the bearing plate into the rockbolt-setting hole. Since the projecting part and the bearing plate are disposed on a sprayed concrete layer, a projection height of the rockbolt is remarkably decreased. Consequently, lining concrete is applied onto the sprayed concrete layer with ease, and the bedrock or ground is reinforced with high reliability.