Influence Mechanism and Parameter Optimization of 40° Wedge-shaped Reaming Length on Mechanical Bearing Characteristics of Anchorage System

Abstract

In deep roadways with soft surrounding rock, the anchorage section of conventional cylindrical rock bolts relies on the bonding and friction at the interface between the anchoring agent and the surrounding rock for load transfer, which is prone to issues such as localized stress concentration in the anchoring agent, rapid development of plastic damage in the surrounding rock, and interface debonding failure. These problems make it difficult for the ultimate anchoring force of the bolt to meet the support requirements under high in-situ stress conditions. This study systematically quantifies the coupling relationship among the 40° wedge-shaped reaming length, anchoring force, and surrounding rock damage. A three-dimensional bolt–anchoring agent–surrounding rock numerical model was established using ABAQUS. With the wedge-shaped reaming angle fixed at 40°, five groups of reaming length conditions—4 cm, 6 cm, 8 cm, 10 cm, and 12 cm—were set up for uniaxial pull-out simulations to reveal the strengthening mechanism of 40° wedge-shaped reaming anchorage. The simulation results reveal that reaming length plays a significant role in modulating the mechanical state of the anchoring system. For short reaming lengths (4–6 cm), the reinforcement effect remained limited and the anchoring agent stress was highly localized near the wedge tip. In the medium range (8–10 cm), the stress within the anchoring agent became more evenly distributed over the anchorage length, while plastic damage in the surrounding rock remained dispersed and non-interconnected; under these conditions, the bolt anchoring force showed the largest improvement, exceeding that of conventional straight-hole bolting by more than 42%. Once the reaming length surpassed 10 cm, the plastic zone in the surrounding rock became interconnected and softened, and the incremental gain in anchoring force diminished markedly. Based on the mechanical response and overall load-bearing performance of the system, 10 cm is identified as the optimal reaming length for the 40° wedge-shaped configuration. These results provide a quantitative reference for designing high-pressure water-jet reaming parameters in deep soft-rock roadways.