Abstract:
Cable bolts are the primary support material for controlling the surrounding rock in underground coal mine roadways. During their service life, cable bolts not only bear high stress loads but are also affected by the harsh corrosive environment. Consequently, stress corrosion cracking (SCC) resulting from the coupling effect of stress and corrosion poses a significant threat to their service reliability in underground coal mines. Among various factors, mine water is a key factor that induces cable bolt corrosion. To investigate the influence of different types of mine water on the stress corrosion behavior of cable bolts, electrochemical impedance spectroscopy (EIS), electrochemical polarization technology, laboratory immersion accelerated corrosion tests and microscopic morphology scanning methods were used to characterize the electrochemical behavior and corrosion evolution characteristics of cable bolts under varying pH levels, SO
42− and Cl
− concentrations in mine water. Overall, the study revealed the SCC mechanism of cable bolts and elucidated the fracture modes of SCC. The results indicate that within the pH range of 2 to 10, the corrosion rate of the cable bolts initially decreases and then increases as the pH increases. Furthermore, pH influences the type of corrosion reactions on the cable bolts. Under acidic conditions, the nucleation of SCC cracks is more likely to occur. The influence of SO
42− and Cl
− concentrations in mine water on cable bolt corrosion follows a similar pattern: as the ion concentrations increase, the corrosion rate gradually increases, facilitating SCC crack initiation. However, the sensitivity of the SCC rate to concentration changes varies across different ion concentration ranges. Anodic dissolution and hydrogen-induced cracking are the two primary mechanisms for cable bolt SCC. The initiation of SCC cracks in cable bolts occurs through three stages: pit initiation, pit growth, and crack nucleation. The fracture surface of the SCC failure of cable bolts exhibits a stepped failure mode, with three typical regions: the crack initiation zone, propagation zone, and final fracture zone. Finally, based on the three dimensions of "material, environment, and stress," control strategies are proposed to prevent cable bolt SCC.