Abstract: Prestressed rock bolt plays a crucial role in geotechnical anchoring engineering thanks to its excellent stability and huge economic benefits. The long-term performance of prestressed rock bolt, however, has been degrading due to the aggressive corrosion environment of surrounding rock and soil. To investigate into the corrosion mechanism of prestressed rock bolts in simulated geotechnical environments, we examined the time-varying behaviors of corrosion damage of prestressed rock bolts under weak acid and oxygen-ventilated conditions based on electrochemical impedance spectrum and electrochemical polarization curve via indoor accelerated corrosion test, and further analyzed the relationship between anchoring force and corrosion rate of prestressed rock bolts. Results revealed no evident passivation of prestressed rock bolts during the experiment. In pre-immersion stage with no oxygen, the electrochemical impedance spectrum of prestressed rock bolt was a large tolerance arc; controlled by charge transfer, the corrosion of prestressed rock bolt was not obvious, and the impedance decreased gradually with time. With oxygen ventilated at low rate, the corrosion of prestressed rock bolt was controlled by both charge transfer and diffusion process; at high-rate of oxygen ventilation, corrosion was controlled merely by diffusion process and appeared earlier with the growth of oxygen flow rate. In conclusion, the corrosion resistance of prestressed rock bolt did not always attenuate with the increase of oxygen flow rate, and the correlation between loss of anchoring force and corrosion rate was weak in the present test.

Key words: prestressed rock bolts, corrosion damage, electrochemical impedance spectroscopy, polarization curve, oxygen-ventilated environment, anchoring force loss