Bond length and interface failure mechanism of anchor cable under continuous radial pressure conditions

The anchoring capacity of the anchor cable is closely related to the bonding length and radial pressure conditions. Through field pull-out tests, theoretical analysis, numerical simulation, and industrial tests,this study clarifies the relationship between radial pressure and bonding length for the ultimate pullout force and reveals the microscopic failure process of the resin-rock interface in the anchoring system.The results show that the ultimate load increases with the increase of bonding length in three different stages: rapid, slow, and uniform growth. The new mechanical model developed considering radial pressure describes the inverse relationship between radial pressure and the plastic zone on the bonding section, and quantifies the reinforcing effect of confining pressure on the anchoring force. During the pull-out process of the anchor cable, the generation of failure cracks is in the order of orifice, bottom,and middle of the hole. Radial pressure can effectively enhance the ultimate pull-out force, alleviate the oscillation increase of pull-out force, and inhibit resin cracking, but will produce an external crushing zone. It also reveals the synergistic effect between bonding length and radial pressure, and successfully carries out industrial tests of anchor cable support, which ensures the stability of the stope roof and provides an important reference for the design of anchor cable support in deep high-stress mines.