应变软化围岩中预应力锚杆与锚索组合锚固模型OA

To address the challenge of combined anchorage using prestressed bolts and cables in strain-softening tunnel surrounding rocks,a mechanical analytical model integrating the rock mass,bolts,and cables was developed based on the Mohr-Coulomb failure criterion and the delayed anchorage mechanism.In this model,the cable extends into the elastic zone,while the bolt penetrates the elastic,plastic-softening,and residual zones.Closed-form solutions for stress,strain,and displacement under various conditions were derived and validated through FLAC3D numerical simulations,demonstrating high consistency and confirming the model's validity and accuracy.Subsequently,a systematic investigation was conducted on the influence of parameters such as prestress level,anchorage length,cross-sectional area,and spacing on the deformation control and support performance of the surrounding rock.The findings indicate that increasing prestress significantly suppresses rock deformation.However,an optimal match between bolt and cable prestress is essential,as mismatched combinations(low-high or high-low)are effective.Moreover,the bolt prestress should exceed a critical threshold.Anchoring bolts within the plastic-softening zone yields superior displacement control,whereas extending cables beyond the elastic zone offers limited additional benefits.Reducing the spacing between bolts and cables enhances the overall support stiffness,but the marginal benefits diminish below a certain critical spacing.Furthermore,the bolt diameter has a more significant impact on the combined support performance than the cable diameter.These conclusions provide a theoretical foundation for optimizing combined support schemes in strain-softening surrounding rocks and offer practical guidance for engineering applications.