Abstract
This study uses the two-dimensional finite-discrete element method (FDEM) to examine how rib spacing and confining stress affect the resin bonding performance of rock bolts. Tensile tests were simulated for bolts with a fixed rib angle of 75° and rib height of 1.5 mm, but with rib spacings of 6 mm, 12 mm, and 18 mm, under confining stresses of 2, 10, 20, and 30 MPa. Increasing the rib spacing can lower the confining pressure threshold for the transition from parallel shear failure to wedge failure. At 2–20 MPa confining stress, the 6 mm rib spacing bolt shows the poorest bonding, failing through parallel shear at the bolt–resin interface. The 12 mm spacing produces a mix of parallel shear and dilatational failure, yielding better bonding, while the 18 mm spacing achieves the best performance by promoting dilatational and wedge-shaped resin failure. At 30 MPa, all bolts tend to fail by wedge failure at the rock - resin interface, and their bonding performances become similar, although localized parallel shear still occurs near some ribs of the 6 mm bolt. The findings of this study can serve as a reference for the rib profile design of rock bolts at varying excavation depths.