岩石波速与损伤演化规律研究

WAVE VELOCITY AND DAMAGE DEVELOPMENT OF ROCK

岩石波速随应力的变化对研究损伤演化具有重要意义。采用颗粒流程序建立9种不同模型,在模型内设置激发源和接收器,通过对激发源施加速度脉冲并记录接收器信号模拟波的传播与衰减,可以得出:配位数与孔隙率呈线性变化关系,波幅衰减与枝矢量分布直接相关,波速主要受孔隙率、配位数张量和刚度张量影响。模拟岩石双轴压缩应力–应变过程中轴向和侧向波速,微裂纹主要沿轴向分布,相比剪切裂纹,张拉裂纹优势导向与轴向夹角较小,且随着裂纹的增多,波速及枝矢量分布各向异性逐渐增大。波速变化的内在原因是新接触点的形成、黏结断裂和接触点的分开,波速变化依赖于刚度张量相应分量的平方根,二者变化规律基本保持一致。通过刚度张量及枝矢量分布变化确定损伤特性及导向,是一种量化波速与损伤的新方法,可为损伤演化规律研究提供参考。

Variation of wave velocity with stress in rock is very significant for the study of damage development. Nine different models were set with the particle flow code(PFC) to simulate the processes of wave propagation and attenuation,in which a velocity pulse was applied to the transmitter and the average velocity was recorded with the receiver. It was revealed that the coordination number was in linear relationship with the porosity. The branch vector distribution was directly related to the amplitude attenuation. Moreover,the wave velocity was mostly affected by the porosity,coordination number tensor and stiffness tensor. The stress-strain process was simulated under biaxial compression to explore the wave propagation. The micro cracks were mainly distributed along the axial direction. In comparison with the shear cracks,the angles between the dominant orientation of the tensile cracks and axis are smaller. With the increase of micro cracks,the anisotropic degree of wave velocity and the distribution of branch vector increased gradually. It was proved that the intrinsic reasons of the velocity variation were the formation of new contacts,the breakage of bonds and the separation of contacts. The wave velocity was essentially consistent with the square root of the corresponding component of stiffness tensor. It was a new method to quantify the damage and wave velocity through analyzing the stiffness tensor and branch vector distribution,which provided reference for the study of damage development.