THE BEHAVIOUR OF FULLY-BONDED ROCK BOLTS IN THE KIELDER EXPERIMENTAL TUNNEL

The article illustrates the features of fully-bonded rock bolt behaviour and gives results from instrumented rock bolts used in the Kielder Experimental Tunnel. Based on these results it is concluded that (1) the behaviour of rock bolts can be described in terms of anchor and pick-up length, (2) there is a wide range of behaviour of similar bolts in the same rock, (3) unsatisfactory behaviour is associated with short anchor length, (4) tightening the nut on the rock bolt increases the anchor length at the expense of higher bolt loading, and (5) at rock bolt failure, shear stress passes through a maximum to a lower constant value. /TRRL/