Experimental study on corrosion mitigation and shear behavior of novel repairable rock bolts

Based on the concept of repairable anchorage for post-damage performance recovery and corrosion protection in jointed rock masses, this study develops novel repairable structures in the form of rock bolts: the extrusion-crushing repairable (ECR) bolt and the hot-melt repairable (HMR) bolt. Chloride wet–dry cycling tests and double-shear tests were conducted on separate groups of double-jointed rock mass specimens to investigate their anticorrosion effectiveness and restoration capability. Preliminary results indicate that both repairable bolts can release repair materials after damage to partially restore sealing conditions, suppress corrosive ingress, and enhance shear resistance. Specifically, the ECR bolt demonstrated the potential for superior corrosion resistance, achieving higher peak shear load and greater external work to peak load under the tested conditions. This improvement may be associated with the infiltration and adhesion of the released polyurethane–ethyl acetate repair agent, which helps seal damaged regions and restore grout integrity over a wider area. In contrast, the HMR bolt provides localized sealing and partial reinforcement through thermally activated melting of EVA adhesive, leading to comparatively moderate enhancements in corrosion resistance and shear capacity. Observations of the failure characteristics further elucidated the reparative mechanisms and the differences in mechanical responses among the bolt systems. This work suggests that integrating repair functionality into rock bolting systems may provide a promising approach for mitigating damage and corrosion in rock engineering.