Experimental investigation of corrosion-induced degradation of rockbolt considering natural fracture and continuous load

Corrosion of rockbolt significantly affects the long-term serviceability of anchorage structures, resulting in premature failure of rock engineering. The corrosion and degradation mechanism for mortar grouted rockbolt is far from clear. In this paper, comprehensive experiments were carried out to investigate corrosion-induced degradation of rockbolt considering natural fracture and continuous load. Concrete-mortar-rockbolt specimens with an initial crack at different locations were made. Continuous axial loads were applied to the rockbolt by a puller system. The electrochemical method was employed to accelerate rockbolt corrosion. The bond — slip relationships for corroded specimens were obtained by the direct pull-out test of rockbolt. Further, the effects of natural fracture and continuous load on the corrosion characteristics, corrosion mechanism and bond performance degradation of rockbolt were discussed. Results show that corrosion of rockbolt significantly reduces the bond strength and critical slip displacement of rockbolt. The bond strength for the rockbolt with a corrosion degree of 3.45%–4.98% reduces by 39.5%–65.8% compared with that before corrosion. Corrosion of rockbolt is more prone to occur near the natural fracture. The closer the natural fracture to the loading end, the more severe the corrosion-induced bond degradation. The larger the axial load, the more significant the corrosion degradation.