基于修正莫尔-库仑准则的围岩瞬态卸荷塑性变形分析

Research on Transient Unloading-Induced Plastic Zone in Surrounding Rock Based on Modified Mohr-Coulomb Criterion

将卸荷视为动态过程,采用包含拉伸截断和帽盖模型的修正莫尔-库仑准则,对不同开挖形状和应力状态条件下围岩瞬态卸荷塑性区进行了分析.研究结果表明:瞬态卸荷可导致自由面附近产生塑性变形,造成围岩损伤弱化甚至破坏;拉伸应力是造成围岩动态卸荷破坏的重要因素;塑性变形随着埋深的增加而增大;最大压应力方向易于产生塑性变形,以拉伸变形为主,当初始应力满足一定条件时,最小压应力方向将产生严重压剪塑性变形;从卸荷的角度考虑,巷道断面曲率较大为宜,尽量避免直线形边界.

Taking the unloading as a dynamic process, the plastic zone generated from different excavation sections and in-situ stress conditions due to transient unloading was analyzed using modified Mohr-Coulomb criterion including tension cut-off and elliptic cap models in surrounding rock. The numerical results indicate that transient unloading will cause plastic deformation in the vicinity of excavation perimeter. The plastic deformation increases with the increase of depth and in-situ stress. Tensile stress is a key factor in accounting for the surrounding rock plastic deformation during transient unloading. The plastic deformation direction coincides with the maximum compressive principal stress. But it can induce serious compressive deformation in the minimum principal stress if the in-situ stress satisfies certain condition. The bigger the section curvature is, the smaller the plastic deformation becomes, so it is better to avoid linear boundary.