Characterisation of stress corrosion durability and time-dependent performance of cable bolts in underground mine environments

Premature failures of cable bolt caused by stress corrosion cracking (SCC) has been more and more often observed with the increasing depth of underground mines. Investigating and predicting this failure are critical in maintaining and accessing the integrity of the reinforcement system. In this study, with application of the designed SCC-AE testing system, the SCC failure processes of cold-drawn cable bolts used in underground reinforcement system was investigated using the acoustic emission (AE) techniques in simulated underground conditions. Damage evolution of the specimens was monitored with AE in real-time. The scanning electron microscopy was adopted to examine the fractographic features of the failed specimen. Through the integrated analysis of specimens’ elongation, the evolution of acoustic activities and fractographic features, three different stages during SCC failure processes were determined including cracks initiation due to the local corrosion, cracks propagation characterised as tear ridges appearance and fast fracture failure evidenced by the shear lips. The parameters of elongations, AE signals in each failure stage were investigated and the SCC propagation rates were determined. As a result, this study confirms the AE technique in combination with the designed testing system can give important insights into the SCC failure as well as the possibilities of real-time SCC monitoring in underground reinforcement systems.