Stress diffusion model of anchor bolts in rectangular tunnel roof and reinforcement mechanism of surrounding rock
In China,coal mining primarily relies on underground extraction,resulting in the annual excavation of about 12 000 kilometers of massive tunnels,with over 90％using rock bolts and cable bolts for support.This study introduces a stress diffusion model for rectangular tunnel roof rock bolts,considering finite boundary conditions and stress superposition principles.It derives formulas for additional stress from bolt pre-tension and proposes a mechanical model for rock mass reinforcement.FLAC3D simulations validate the model,which is then used to study how bolt parameters affect reinforcement.Key findings show that in bolt groups,minimum vertical additional stress occurs between bolts,anchored body strength increases linearly with pre-tension,reinforcement decreases non-linearly with increased bolt spacing,and exhibits a peak with bolt length,indicating that simply increasing length doesn't always improve reinforcement.
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