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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.
The unloading is regarded as a dynamic process, and the modified Moiré-Coulomb criterion including tensile truncation and cap model is used to analyze the transient unloading plastic zone of surrounding rock under different excavation shapes and stress conditions. The results show that : Transient unloading can lead to plastic deformation near the free surface, resulting in the weakening or even damaging surrounding rock damage. Tensile stress is an important factor that causes the dynamic unloading damage of surrounding rock. The plastic deformation increases with the increase of the buried depth. The maximum When the initial stress satisfies a certain condition, the direction of the minimum compressive stress will produce a severe compression shear plastic deformation; From the unloading point of view, the curvature of the tunnel section is appropriate, Try to avoid linear boundaries.