基于颗粒-界面-基体模型圆形巷道围岩中应力与应变演变分析

视岩石将由3种成分构成：颗粒、界面和基体，采用FLAC模拟圆形巷道开挖之后围岩中的剪切应变增量、最小及最大主应力的分布及演变规律。在静水压力条件下，剪切应变增量的高值区主要分布在软弱的基体之中，形成了相互交织的剪切带网格，而最小主应力的高值区（环向高受压区）主要分布在相互接触的颗粒之中，形成了若干圆环。当侧压系数不等于1时，剪切带网格的轮廓呈三角形。颗粒尺寸的增加使剪切带的数目降低，长度增加，最小主应力的高值区的数目降低，间距增加；颗粒尺寸大时的结果与分区破裂化现象相近。由此提出一种可能的裂化机制：节理岩体中的若干岩块由于自组织作用而被挤成1圈，如果应力水平足够高，就可以形成多条环向的被未破坏区隔开的破坏区。

Evolution of stress and strain in surrounding rock of a circular tunnel based on a grain-interface-matrix model

Rock is treated as a compound including three component parts: grain, interface and matrix. FLAC is used to model the distribution and evolution of the shear strain increment, the minor and maximum principal stresses in the surrounding rock after a circular tunnel is excavated. Results show that in hydrostatic pressure, higher shear strain increments are mainly distributed in the soft matrix, forming an intersecting shear band network. However, higher minor principal (loop higher compressive) stresses are found at grains, generating several annular or ring regions. Larger granular sizes lead to fewer and longer shear bands, less number of regions with higher minor principal stresses and larger spacing between them. When the lateral confining pressure coefficient is not 1, the envelope of the shear band network exhibits two triangles at two opposite sides of the tunnel. At larger granular sizes, the results are similar to the zonal disintegration phenomenon in the tunnel surrounding rock at depth. Thus, a possible mechanism is proposed for the phenomenon. In jointed rock mass, several rock blocks are compressed together to form a ring in the loop direction of the surrounding rock due to the self-organization. If the stress level is high enough, several loop cracks isolated by zones without failures can be formed.