深埋大理岩三轴压缩渐近破坏裂纹扩展特征研究

为深入研究深埋大理岩渐进变形破坏过程中裂纹扩展特征,基于常规三轴室内试验完成数值模拟参数标定,利用PFC_3D^{颗粒流模型对深埋大理岩开展}25MPa、50MPa、80MPa三种不同围压下的裂纹扩展数值模拟试验,根据大理岩加载过程中微裂纹演化状态参数,定义三种特征应力,并据此展开深埋大理岩渐进破坏过中的宏、细观破坏特征及其对应裂纹扩展特征的规律研究。结果表明：(1)。室内试验与数值模拟的应力应变曲线相吻合,峰值应力相差较小,破坏形式与室内试验一致,故数值模拟参数标定合理。低围压下应力应变曲线出现的应力降最为明显,高围压下出现的应力降最小。(2)依据总裂纹、张拉裂纹和剪切裂纹扩展数量演化曲线斜率变化规律,将深埋大理岩渐进破坏过程划分为弹性压缩阶段、裂纹稳定扩展阶段、裂纹加速扩展阶段和峰后残余阶段四个阶段,根据裂纹数量定义三个特征应力点。(3)随着围压的增加,深埋大理岩达到起裂应力σ_ci时裂纹从两端开始萌发,加载至损伤应力σ_cd点时向中间扩展,达到峰值应力σ_c点时在宏观破坏面附近扩展、增生,加载至峰值点后70%峰值应力点时最终形成以剪切破坏为主的贯通宏观破坏面。(4)随着围压的增加,裂纹出现的范围更广,贯通性减弱,峰值应力σ_c点处产生的裂纹对宏观破坏产生的影响更为剧烈,峰后残余阶段张拉裂纹发育更明显。

STUDY ON CRACK PROPAGATION CHARACTERISTICS OF DEEP MARBLE UNDER TRIAXIAL COMPRESSION

In order to deeply study the characteristics of crack propagation in the progressive deformation and failure process of deep-buried marble, the numerical simulation parameters were calibrated based on the conventional triaxial laboratory test, and the PFC_3D ^{particle flow model was used to car}ry out the numerical simulation test of crack propagation of deep-buried marble under three different confining pressures of 25, 50, and 80 MPa. According to the state parameters of microcrack evolution during the loading process of marble, three characteristic stresses are defined, and based on this, the macro and micro failure characteristics of the progressive failure process of deep marble and the law of its corresponding crack propagation characteristics are studied. The results show that: (1) The calibration of numerical simulation parameters is reasonable. The stress-strain curves of the indoor test and numerical simulation are consistent, and the difference of peak stress is small, which is consistent with the indoor test. The stress drop in the stress-strain curve under low confining pressure is the most obvious. With the increase of confining pressure, the post-peak stress drop is smaller. (2) Based on the evolution law of crack propagation quantity and the slope change of total crack, tension crack and shear crack propagation quantity evolution curve, the progressive failure process of deeply buried marble is divided into four stages: