ROCK BOLT WITH ELONGATION MEASUREMENT MEANS

The invention provides a strain measuring rock bolt which includes a yielding rod of a malleable material which extends between a distal end and a proximal end, a bore which extends through the rod between the distal and proximal ends, a measuring device which is at least partially contained within the bore, which includes a sweeping or indicatory element and a graduated member, wherein fixed to the rod is either the element or the graduated member and attached distally to the rod is either the member or the element respectively to allow movement of the element relatively to the member when the yielding rod elongates under strain and wherein movement of the element relatively to the member manifests as a change in a physical or electronic parameter, which change is measured and communicated as an output.