Abstract: The present invention discloses a tube (14) for rock bolts having either a cable tendon or a rod tendon. The tube is deformed to permit the tube to be coiled and yet also provide good keying between the tube and grout. In addition, a fitting (26, 46) for the rear end of the bolt is disclosed in which a grouting orifice (31) communicates with a cable passageway (34). Furthermore, the use of two or more cable anchors (57) at the far end of the bolt is disclosed where the bolt is intended to be used in poor ground conditions, such as sandstone.

Abstract: The present invention discloses a rock bolt having a tendon (1, 201) which is able to yield and thereby control movement of unstable rock strata into which the bolt is installed. The tendon has a portion which is provided with a grout slippage mechanism, preferably in the form of a tube (8) which surrounds the tendon. A two part grout anchor (10, 100, 200) is clamped to the tendon. The grout anchor is embedded in grout and is therefore essentially immovable. The tendon passing through the anchor is worked and thereby dissipates energy. The tendon can be either a multi-strand cable (1) or a solid bar (200). Various forms of anchor (10, 200) are disclosed with either complementary recess(es) (14) and protrusion(s) (15) or opposed protrusions (115) which form pinch point(s). A one piece grout anchor (300) is also disclosed.