ABSTRACT
As more complex geological conditions are encountered in deeper underground mines, maintaining the safety and productivity of the mines has become more challenging. This requires installation of long-lasting high performance anchoring systems in underground mines. Cable bolts are particularly attractive for such applications since they have higher mechanical properties than conventional rockbolts and, being flexible, can anchor to greater depths into the rock strata. Despite substantial improvements in cable bolting technology over the years, catastrophic failure is still being reported. In this study, two failed cable bolts from an underground coal mine were collected and examined to identify their failure mechanism. Magnetic particle inspection, metallographic analysis and Scanning Electron Microscopy (SEM) were used to characterise the crack path and fracture surface of the wires from the failed cable bolts. A step-like crack path and Tearing Topography Surface (TTS) similar to those reported previously for failed reinforcing cables used as prestressed tendons in civil engineering structures were observed. These features indicated that the cable bolt failures were caused by Hydrogen Induced Stress Corrosion Cracking (HISCC).
