Patent ID: 8337120

Claim:
A rock bolt for being grouted in a borehole in a rock, said rock bolt comprising: an elongate cylindrical solid stem with a threaded portion at a borehole surface portion of said stem, said threaded portion provided with one or more nuts and one or more washers, sheaves or face plates arranged for pre-tensioning the rock bolt in the borehole; said stem comprising three or more lengths of stem portions, each of said three or more lengths of stem portions being followed by an integral anchor, each of said integral anchors having a length shorter than a length of each of said three or more stem portions, each of said integral anchors being separated from each other along a length of said stem; said anchors for being locally anchored relative to corresponding local borehole wall portions for taking up load arising due to rock deformation; and said three or more stem portions having a smooth surface for slipping relative to the borehole or grout within the borehole, so that each of said three or more stem portions constrains local rock deformation through elongation of said three or more stem portions between adjacent pairs of said integral anchors.