ABSTRACT
It is important to know the generated axial force distribution along a rockbolt in evaluating the reinforcement effects of rockbolting or facebolting. Hence, the measurement of the axial forces of rockbolts has been routinely performed at some sections of each tunnel. Friction-anchored expanded-steel-tube-type rockbolts (referred to as EST rockbolts henceforth) have been used where the early-time function is required and/or the loss of grout due to water ingress is expected. In addition, they have been used for facebolts since excavation machines such as roadheaders can easily cut them. Recently, long facebolts composed of thread-connected EST rockbolts are also used (e.g.
