非饱和多孔介质层中Love波频散特性

为建立更准确的地层反演模型,基于非饱和多孔介质本构关系,用连通率处理上面两层间的边界条件,理论推导出三层非饱和多孔介质中Love波的频散方程,计算分析多阶模态Love波频散曲线。结果表明,Love波第1阶模态没有截止频率,对2阶以上模态,阶数越高截止频率越大。各阶模态的Love波最大速度趋近半空间层的横波速度,而最小速度趋近第1层横波速度。Love波速曲线以第2层横波速度为界分为上下两簇,各模态均在第2层横波波速处衔接。模态不同,衔接处曲线的光滑程度不同,模态越高,光滑程度越好。对各参数的敏感性分析表明,孔隙度、饱和度、连通率、黏滞系数和渗透率的变化对Love波相速度影响敏感性依次减小。

Dispersion characteristics of Love wave in unsaturated layered porous media

Using connectivity factor to handle the boundary condition between the two upper layers, the Love wave dispersion equation for three layers in an unsaturated porous media was derived based on the constitutive relations, and then the multi-mode Love wave dispersion curves were calculated numerically. The results indicate that, for the second or higher order Love wave modes, the higher the mode order, the larger the cut off frequency, in contrary to the fundamental mode Love wave which doesn ''t have cutoff frequency. The maximum velocity of Love waves for all the modes asymptotically reaches the shear wave velocity of the half-space, while the minimum velocity reaches the shear wave velocity in the top layer. The Love wave velocity curves for all the modes are separated by, but are also linked to the shear wave velocity in the second layer. The smoothness of the velocity curves is controlled by the mode number:the higher the mode, the better the smoothness. Analyses show that the sensitivity of Love wave phase velocity to different parameters decreases with the order of the following parameters: porosity, saturation, connectivity factor, viscous coefficient and permeability.