Load transfer mechanism of corroded rockbolt-grouted structures under low strain rate: experimental and theoretical analysis

This paper explores the engineering failure of corroded rockbolt-grouted structures under dynamic disturbance. Through indoor testing, the influence of a low strain rate on the load transfer behaviour is examined to elucidate the bond–slip mechanism. The load transfer principle is used to construct the load transfer equation of rockbolt considering the effects of strain rate and corrosion, and the distributions of axial force and shear stress in corroded rockbolts are analyzed under low strain rates. The results indicate that, at high temperature, the corrosion rate of the rockbolt accelerates, and the cracks at the grouted interface expand rapidly, which makes the rockbolt change failure mode. Under a given load, a higher corrosion degree accelerates the axial force decay rate and makes the distribution of the interface shear stress more uneven. The axial force and shear stress of the rockbolt tend to increase with the strain rate, which increases the load transfer efficiency of the rockbolt and makes it more likely to enter the softening phase. The established load transfer model realistically expresses the effects of corrosion and low strain rate on the load transfer mechanism during rockbolt pull-out, and the test results verify the veracity of the model.