Stress corrosion cracking of cable bolts in tunnels: An in-situ testing approach

Abstract

Premature failure of cable bolts in underground tunnels is a major concern for the mining and civil industries. The unexpected failure of cable bolts in tunnels can threaten the safety of excavation operations and cause subnational economic losses. In this study, an in-situ testing method was developed to identify the cause of failure in the environment where the cable bolts are installed. The testing was conducted in two underground mine tunnels in Australia. The coupon made from non-galvanised and galvanised cable bolt wires with multiple stressed sections were installed in the tunnel roof, allowing direct exposure of coupons to different rock strata environments. The coupons were retrieved from the tunnels after almost ten months and analysed for corrosion. Results from both tunnels showed the occurrence of stress corrosion cracking (SCC) in both non-galvanised and galvanised coupons. The cracking predominantly occurred in the sections exposed to claystone layers. The framework developed in this study can be applied to different regions of any underground spaces to assess the propensity of the environment to cause premature reinforcement failure.