When mining at great depth, on going time-dependent deformations or unexpected rock failures due to high stress may be experienced. In order for ground support to survive the large displacements and control the rock mass, yielding cable bolts have been developed in South Africa and Australia. Decoupling of a significant length of the strand from the cement grout to allow for large displacement of the reinforc ement element means the system is effectively a point anchored system. Consequently, for cable bolts the performance of the barrel and wedge anchor becomes critical to achieve effective load transfer. Failure by sliding of anchors relative to the strand under low loads has been observed in several underground mines in the Eastern Goldfields of Western Australia. This is attributed to a combination of poor installation practices and corrosion. The results from a number of cable bolt barrel and wedge combinations placed within a corrosion chamber and subsequently pull tested to determine the load-displacement response are examined. The results show that after 7 months in the corrosion chamber the barrel and wedge used with a yielding cable bolt failed at loads significantly less than the strand capacity. The service life can be extended to more than 10 months with the application of barrier corrosion protection. On the other hand, galvanising of barrel and wedge anchors is not recommended.
Corrosion of barrel and wedge anchors and the consequences for the entire cable bolt performance is poorly understood, despite the common use of cable bolts in Australian underground mines since the 1970s. The use of barrel and wedge anchors to restrain plates, straps and mesh in cable bolt reinforcing applications commenced in the early 1980s in Australian mines . Recent developments in cable bolt design have meant an increased reliance on anchors to be serviceable for long periods of time, especially for applications where the strand is decoupled from the cement grout. Anchor failures after short time durations and under low loads have been observed in several underground mines in the Eastern Goldfields of Western Australia (e.g. Fig. 1). Failure is often characterised by the barrel and wedge remaining intact after being found on the floors of drives with no evidence of strand rupture . Approximate