Dynamic mechanical responses and debonding failure mechanisms of bolt-resin-rock anchoring system subjected to cyclic shear loading

This study delves into the mechanical responses and debonding mechanisms of bolt-resin-rock composite anchoring system subjected to cyclic shear loading. A systematic analysis was conducted on the effects of initial normal load (Fsd), cyclic shear displacement amplitude (ud) and frequency (f), as well as rock types on shear load, normal displacement, shear wear characteristics, and strain field evolution. The experimental results show that as Fsd increases from 7.5 kN to 120 kN, both peak shear load and residual shear load exhibit an increasing trend, with increments ranging in 1.98% ~ 35.25% and 32.09% ~ 86.74%, respectively. The maximum shear load of each cycle declines over cyclic shear cycles, with the rate of decrease slowing down and stabilizing, indicating that shear wear primarily occurs at initial cyclic shear stage. During cyclic shearing, normal displacement decreases spirally with shear displacement, implying continuous shear contraction. The spiral curves display sparse upward and dense downward, with later cycles dominated by dynamic sliding along the pre-existing shear rupture surface, particularly evident in coal. The anchoring system's bearing capacity varies with rock types: governed by coal strength in coal, resin-rock bonding in sandstones#1 and #2, combined resin strength and resin-rock bonding in sandstone#3, and resin strength and bolt-resin bonding in limestone. Cyclic shear loading induces anisotropic interfacial degradation, characterized by escalating strain concentrations and predominant resin-rock interface debonding, with damage severity modulated by rock types.