The environmentally induced corrosion failure of cable bolts in underground coal mines

The failure of cable bolts, made from high carbon cold-drawn steel wires, is frequently observed in underground coal mines. Hydrogen-induced stress corrosion cracking (HISCC) is known to be the main mechanism of such a failure. The groundwater and geomaterials (mixture of coal and clay) collected from the affected mines have not been found to be corrosive. In this study, we examine the effect of sulfate-reducing bacteria (SRB), which exist in affected mines, on the failure of cable bolts. We make stressed coupons from cable bolt wires and test the coupons in different solutions containing SRB. We find that the hydrogen sulfide produced by SRB promote hydrogen diffusion into the steel and causes HISCC while the steel is under constant load. The fractures in failed coupons show similar features to those failed in underground coal mines. This study provides insights into the role of microorganisms in the failure of underground structures. We recommend future studies to develop prevention measures to stop hydrogen diffusion into steel or microbial activities around the bolts.