饱和岩石的各向异性及非线性黏弹性响应

ANISOTROPY AND NONLINEAR VISCOELASTIC BEHAVIOR OF SATURATED ROCKS

在MTS伺服压机上对不同饱和状态的砂岩、大理岩标本进行了垂直层理和平行层理两个方向的正弦波加载试验 ,研究了饱和岩石的各向异性及非线性黏弹性行为 .在最大载荷低于岩石的屈服点时 ,获得的衰减、杨氏模量、泊松比、波速都表现出显著的各向异性 ,同时它们还具有较明显的应变振幅效应和频率效应 .随着应变振幅的增大 ,衰减近似呈线性增长 ,杨氏模量和泊松比近似呈线性下降 .在 0 .0 0 5— 4Hz频段内除衰减不明显依赖频率以外 ,杨氏模量、泊松比、波速对频率的依赖性都较强 ;当频段扩大到 1 5Hz时 ,这 4个参数都表现出较强的频率效应 .饱和岩石的衰减、杨氏模量、泊松比、波速均随饱和液体的黏滞系数增大而增大 .

Low-frequency uniaxial stress cycling tests were conducted on sandstone and marble in different saturation condition to find the possible anisotropic and nonlinear behavior. The results indicate that under yield points the attenuation, Young's modulus, Poisson's ratio and velocities of saturated rocks all display obvious anisotropy and rather apparent strain amplitude effect and frequency effect. As strain amplitude increases, the attenuation increases linearly, while Young's modulus and Poisson's ratio decrease approximately linearly. In the frequency range of 0.005-4Hz the attenuation shows no strong frequency dependence while Young's modulus, Poisson's ratio and velocities depend obviously on frequency. When the frequency range is enlarged to 15Hz all the four parameters show rather strong frequency dependence. The attenuation, Yong's modulus, Poisson's ratio and velocities of saturated rocks increase as viscosity coefficient of the saturant increases.