Advancements in underground engineering reveal improved anchor systems for mining stability and safety.
Researchers have developed a nonlinear convergent model of the anchor structure within the FLAC3D software, enhancing its ability to simulate and analyze anchor behavior under complex geological stress conditions. This new model addresses previous limitations of FlAC3D, which treated anchors as ideal elastoplastic materials without accounting for strength decay during large deformations. The study focused on negative Poisson's ratio (NPR) anchors, which have shown extraordinary mechanical properties and effectiveness during dynamic stress events.
Ground instability is pivotal for safe excavation practices, particularly at great depths where ground pressure, permeability, and disturbances can significantly compromise the integrity of surrounding rock formations. To combat these challenges, researchers introduced various energy-absorbing anchor designs, leading to the evolution of NPR anchors, which outperform conventional Poisson's ratio (PR) anchors significantly. For example, NPR anchors can sustain up to 850 kN of constant working resistance and exhibit exceptional elongation capabilities during plastic deformations.
Through careful numerical pullout tests, the newly developed model verified the accuracy of simulations for NPR anchors by correlatively examining expected engineering conditions with actual performance across both elastic and plastic stages. The new model demonstrates marked improvements, representing real-world conditions more accurately than previous FLAC3D models.
The study also compared two operational mining methods: the traditional 121 method and the newly established 110 method. Notably, the researchers revealed significant discrepancies between the two methods' effectiveness, particularly highlighted by stress distributions observed during simulated back mining operations. Peak shear stresses were found to be 2.48 times higher for the conventional 121 method versus the 110 method, demonstrating the latter's capacity for facilitating improved stability during mining.
Unlike the 121 method—which involves mining with coal pillars creating significant stress concentrations—the 110 method employs pre-splitting, blasting, and strategic reinforcement disallowing reliance on coal pillars. One significant outcome showed the 110 method results in significantly lower vertical stress distributions within roadway support structures, with the stress levels being 1.3 times higher for the 121 method.
The model's potential was validated through thorough inspections of stress distributions outside roadway perimeters, determining shear stresses were up to 6.7 times lower for the 110 method compared to traditional approaches, positioning NPR anchors as integral components to efficient mining operations.
The research exemplifies the advancement of engineering practices aimed at promoting o improvements to both methodology and structural integrity. The development of numerical models like this, which account for realistic failure mechanisms and stress distributions, provides engineers with tools necessary for ensuring safer mining practices.
Overall, the successful application of advanced modeling techniques enables mining engineers to mitigate risks associated with rock stability and improve operational efficiencies encountered during the deep excavation, presenting valuable insights for future practical implementations.