Resin Flow Characteristics and Anchoring Performance of Resin-Anchored Bolts in Soft and Broken Surrounding Rock

Resin distribution in a borehole is critical to the anchoring performance during resin-anchored bolt installation. The distribution characteristics of the resin may be affected by fractures in the soft and broken surrounding rock of the borehole wall. Accordingly, numerical simulations, theoretical analyses, and laboratory experiments were performed to explore the resin flow characteristics and the anchoring performance of resin-anchored bolts in soft and broken surrounding rock. The results indicate that, for resin mixing in soft and broken surrounding rock, the resin and the curing agent rapidly flow into the fractures in the borehole wall during the rotation and advancement of the bolt toward the bottom of the borehole, resulting in resin loss. The amount of resin loss increases with the fracture aperture, number of fractures, and fracture angle, continuously weakening the anchoring performance. With increasing number of fractures, the deformation of the anchoring system before reaching the maximum anchoring force gradually increases. Conversely, an anchoring system with no fractures can quickly play its bearing role and provide a high working resistance. In addition, an improving method of anchoring performance was proposed: grouting reinforcement and borehole wall repair can enhance the strength of the surrounding rock, reduce the fracture aperture and resin loss, and improve the anchoring quality. This paper provides a theoretical reference for the stability control and anchoring quality improvement of soft and broken surrounding rock.