Improvements in rock bolts

摘要

A radially expandable friction bolt (10) for frictionally engaging with the internal surface of a bore drilled into rock strata comprises a generally circular tube (12) defining a longitudinal split (14). The bolt has a first leading end (18) for insertion into a bore and a second end defining a head (16) and includes expander means (40) for expanding the diameter of the tube at least one location along the tube. The expander means comprising first (44) and second (42) expander elements arranged so that relative movement of the two elements causes the diameter of the tube to expand at that location. The first expander element (44) is mounted on a rod (30) which extends along the tube towards the head of the bolt: the second expander element locates between the rod and the tube and is not secured to the tube. A contraction or narrowing (22) is defined in the internal diameter of the tube which limits the movement of the second element towards the proximal end of the friction bolt. I> Mt ~ ~4&r'.X. IN,