Rock bolt

A method of rock bolt operation, comprising:

• providing a rock bolt, the rock bolt comprising:
• an elongate, generally circular tube the tube having a leading end and a trailing end
• an expander mechanism disposed within the tube in a region of the leading end;
• an elongate tendon disposed longitudinally within the tube and in connection at or towards a first end of the tendon with the expander mechanism and in connection at or towards a second and opposite end of the tendon with an anchor arrangement positioned at the trailing end of the tube
• the anchor arrangement including a rock plate for bearing against the surface of a rock body into which the rock bolt is inserted and a couple the tendon being actuatable to actuate the expander mechanism and to remain connected between the expander mechanism and the anchor arrangement while the expander mechanism is actuated;
• and
• the method of operation being characterised in that:
• under tensile loading of the tendon the couple has:
• a. a first mode of operation that allows movement of the anchor arrangement axially away from the trailing end of the tube and enabling further expansion of the expander mechanism and
• b. a second mode of operation that couples the anchor arrangement to the tube preventing further movement of the anchor arrangement axially away from the trailing end of the tube