Study on the Load Transfer and Damage Evolution Characteristics of the Bolt-Grout Interface concerning Bolt Rib Parameters: Based on a Finite-Discrete Numerical Method

Abstract

Revealing the load transfer and failure mechanisms of the bolt-grout interface is crucial for the stability control design of rock mass engineering. Based on laboratory experiments, this study employs a FLAC-PFC coupling numerical simulation method to conduct shear numerical simulations under different normal stress, rib angle, and rib spacing conditions. The study investigates the impact of rib parameters on the load transfer and microscopic damage evolution of the bolt-grout interface. The results show that: When the rib angle is below 45°, the grout tends to climb along the ribs. As the rib angle increases, the normal stress F_n between the grout and ribs gradually increases, leading the grout to adopt a sheared-crush failure mode. When the rib spacing is less than 12 mm, the grout tends to undergo an overall sheared-off failure mode. When the rib spacing is greater than 20 mm, the grout consistently undergoes a sheared-crush failure mode. As the rib spacing increases, the number of ribs gradually decreases, resulting in more intense interactions between each rib and the grout, and a larger damage area around the ribs. With the increase in normal stress, the interactions between the ribs and the grout become more intense, generating more cracks.