Study on the deterioration of bond-slip performance of rockbolt grouted structures under corrosion

In light of the issue that rockbolts are prone to corrosion in deep engineering projects, leading to support failures, this study uses a combination of electrochemical corrosion testing, rockbolt pull-out testing, and numerical analysis to investigate the bond-slip performance and failure mode of rockbolt grouted structures under the effects of corrosion. Specifically, this study aims to clarify the process of damage due to corrosion and the corrosion mechanism of rockbolt grouted structures, as well as construct a bond-slip model for rockbolt grouted structures that accounts for the effects of corrosion. The results of this study indicate that during electrochemical corrosion, hydrogen ions continuously transfer and flow over the rockbolt surface, resulting in the formation of corrosion products adhere to the surface and accelerate corrosion. Under acidic conditions, the concentration of hydrogen ions in the electrolyte gradually increases with time, resulting in an increase in the corroded area on the rockbolt. This leads to a hydrogen evolution reaction, causing the bond strength of the rockbolt to increase first and then decrease. Meanwhile, in a moderately alkaline environment, a small number of the hydrogen ions react with the cathode to form a hydroxide. Accelerates the corrosion rate of the rockbolt, resulting in a gradual decrease in the bonding strength of the rockbolt. Due to the reduced bond strength and stress concentration caused by corrosion, rockbolts are more prone to pull-out failures in acidic conditions and splitting failures in moderately alkaline environments. Once the rockbolt’s corrosion degree reaches 20%, the bond strength of the rockbolt decreases by 44.3% compared to that before corrosion, ultimately leading to breakage of the rockbolt body. The calculated results from the bond-slip model are in good agreement with the test results, accurately representing the bond-slip performance of rockbolt under the combined effects of corrosion time and pH.