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为获取锦屏大理岩的特征强度及破坏过程中损伤演化规律,运用PFC~(3D)模拟大理岩试样并进行单轴、三轴压缩试验,以微裂纹的形态和数量的变化特征来确定大理岩的起裂和损伤强度。当微裂纹数量为峰值强度下微裂纹数量的0.1%,认为出现初始损伤,此时应力为大理岩的起裂强度。单轴压缩试验中,从裂纹形态上观察,将出现基本破裂面的应力定义为损伤强度。三轴压缩试验中,从裂纹数量上观察,将出现裂纹非稳定增长阶段时的应力定义为损伤强度。分析不同阶段出现微裂纹的位置实现了对微裂纹的定位,分析不同模型微裂纹增长量的变化,实现了对微裂纹稳定和非稳定增长的界定,补充了声发射的不足。对比PFC~(3D)模拟和实验室试验得出的大理岩的特征强度,两者特征强度曲线的拟合函数相近。这说明运用PFC~(3D)模拟确定大理岩的起裂强度、损伤强度的方法是一种合理的方法,微裂纹的研究对揭示脆性岩石强度破坏机制具有重要意义。
In order to obtain the characteristic strength of Jinping marble and its damage evolution during the failure process, the PFC 3D simulation of the marble specimen was carried out and the uniaxial and triaxial compression tests were carried out to determine the characteristics of microcrack morphology and quantity Marble initiation and damage strength. When the amount of microcracks is 0.1% of the number of microcracks at peak strength, initial damage is considered, and the stress at this moment is the initiation strength of marble. In the uniaxial compression test, from the crack morphology observation, the stress at which a rupture occurs is defined as the damage strength. Triaxial compression test, the number of cracks from the point of view, there will be crack growth in the unstable phase of the stress is defined as the damage intensity. The location of microcracks in different stages was analyzed to locate the microcracks. The changes of microcracks in different models were analyzed. The definition of stable and unsteady growth of microcracks was realized, which made up for the lack of acoustic emission. Compared with the characteristic strength of marble obtained from PFC 3D simulation and laboratory tests, the fitting function of the two characteristic intensity curves is similar. This shows that using PFC 3D simulation to determine the initiation strength and damage strength of marble is a reasonable method. The study of microcracks is of great significance to reveal the strength failure mechanism of brittle rocks.