真三轴压缩下大理岩强度、变形与损伤特征数值

为研究真三轴条件下岩石的力学行为，采用离散元颗粒流程序，探析不同应力路径下大理岩试样的变形破坏过程、微裂纹演化机制及其中间主应力效应。结果表明：平行黏结模型能较准确地反映大理岩真三轴压缩下力学特性和破坏模式；中间主应力对峰值强度、弹性模量、破坏角和破坏模式演变的影响较为显著；八面体理论可较好地拟合出大理岩真三轴压缩中的破坏应力，所得的破坏强度包络线具有明显线性特征；结合应力-应变曲线形状，该大理岩在压缩过程中裂纹扩展可划分为4个阶段，即线弹性阶段、裂纹稳定扩展阶段、裂纹非稳定扩展阶段及峰后破坏阶段；随着中间主应力增大，应力-应变曲线峰后段的脆性破坏特征变强，试样从拉伸破坏向拉剪混合破坏转变，且中间主应变符号由拉转向压，岩石损伤演化与中间主应力间呈现出“对勾”型趋势。

Numerical study of strength, deformation, and damage characteristics of marble under true triaxial compression

A discrete element particle flow procedure was adopted to investigate the mechanical behaviour of rock under true triaxial conditions. The deformation and damage processes, the intrinsic connection between microcrack growth and evolution, and the intermediate principal stress effects in marble specimens were analyzed under different stress paths. Results show that the parallel bond model could accurately reflect the mechanical properties and damage modes of marble under true triaxial compression. The effects of intermediate principal stress on the peak strength, elastic modulus, failure angle, and failure mode evolution were significant. The octahedral theory could well fit the failure stress of the marble under true triaxial compression, and the obtained failure strength envelope had obvious linear characteristics. On the basis of the stress-strain curve, the crack expansion during the compression was divided into four stages: linear elastic stage, crack stable expansion stage, crack unstable expansion stage, and post-peak damage stage. With the increase in the intermediate principal stress, the brittle failure characteristics of the post-peak section of the stress-strain curve became stronger. The failure modes of the rock specimen changed from tensile failure to mixed tensile-shear failure, and the intermediate principal strain changed from tensile to compression. The evolution of rock damage showed a spoon-shaped trend as the intermediate principal stress changed.