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为对大断面小净距隧道的净距进行全面优化,采用大型有限元软件ANSYS,对不同净距下的大断面隧道施工过程进行数值模拟,研究不同净距下隧道施工过程的围岩应力场和位移场分布情况及支护体系的受力情况,获得隧道净距对围岩应力分布、支护体系受力和断面收敛的影响,再运用层次分析法分析影响因素的目标度,进行一致性检验并确定权重.研究结果表明:大断面小净距隧道在开挖过程中,围岩应力及变形略呈对称状态,先开挖隧道支护受力及围岩变形略大于后开挖隧道,净距越大,对称现象越明显,围岩应力和变形及支护体系的受力越小,围岩及支护体系稳定性越高,综合考虑支护体系安全及围岩稳定等因素,该大断面小净距隧道的最优净距为1.6B(B为开挖净距).
In order to optimize the clearance of tunnel with large section and small clear distance, large-scale finite element software ANSYS is used to simulate the construction process of large-section tunnel under different clearances and to study the surrounding rock stress field And the distribution of displacement field and the supporting system, the influence of tunnel clearance on the stress distribution of surrounding rock, the force of supporting system and the cross-section convergence are obtained. Then, the analytic hierarchy process (AHP) The results show that during the excavation process, the stress and deformation of the surrounding rock are slightly symmetrical. The stress of the first excavation of the tunnel and the deformation of the surrounding rock are slightly larger than that of the post-excavation tunnel. The larger the clear distance is, the more obvious the symmetry phenomenon is. The smaller the stress and deformation of the surrounding rock and the force of the support system, the higher the stability of the surrounding rock and the support system. Considering the security of the support system and the stability of the surrounding rock, The optimal clearance of the tunnel with large section and small clear distance is 1.6B (B is the clear distance of excavation).