Numerical study on the reinforcement mechanism of prestressed bolts based on the reconstruction of coal fracture structures

The presence of structural weak planes severely affects the stability of the surrounding rocks in underground engineering and the safety of deep resource extraction. This study utilized the discrete element method to simulate and reconstruct the fracture network in the surrounding rocks. A model of the anchored solid containing a fracture network was established using a synthetic rock mass approach. Confined compression tests were conducted on anchored models with different support densities and pretension forces. The results indicate that both high support density and high pretension force can enhance the mechanical properties of fractured anchored solids to varying degrees, significantly improving the bearing capacity during the plastic phase. Additionally, high support density and pretension force can notably alter the failure mode of the anchored solid under load, reducing lateral displacement, delaying the initiation of primary fractures, and decreasing the number of newly formed fractures. From the perspective of prestressed load bearing, increasing anchor density or applying a high pretension force facilitates the formation of a wide and high-strength effective compressive stress zone. This in turn reduces the opening and sliding of primary fracture fields, the generation and propagation of secondary fractures, improves the stress state of the anchored solid, and enhances the overall strength of the surrounding rocks within the anchoring range. From the viewpoint of energy absorption and dissipation, increasing anchor support density and pretension force can significantly improve the ability of surrounding rocks to absorb external input energy, enhance the disturbance resistance of the anchored solid, and slow down the release of strain energy. The modeling process and research findings of this study offer valuable insights for analyzing structural failure and stability control in fractured rock masses.