刚度缓变介质中瑞利波特性

基于薄层刚度矩阵方法，研究了瑞利波在3种典型刚度缓变介质中传播特性，并对瑞利波在缓变介质及分层介质中传播特性进行比较。结果显示，无论剖面刚度是缓变还是分层变化，对规则剖面，表面波场基阶模态占主导地位，远场表面波有效相速度与基阶模态相速度接近；对不规则剖面，表面波场中高阶模态影响较大，影响程度及频率范围与剖面刚度变化有关。在缓变介质中，模态相速度高频趋势值高于剖面最小剪切波速介质的瑞利波速，有效相速度趋势值也明显偏离表面介质瑞利波速，这些特性与分层介质不同。研究结果显示，当缓变介质用数量有限的虚构分层来模拟时，表面波频散测试数据与理论值匹配程度及剖面分析精度会受虚构层数量影响。

Behavior of Rayleigh waves in media with smoothly varying stiffness profile

Based on the thin layer stiffness matrix method, the behavior of Rayleigh waves in three typical media with smoothly varying stiffness is studied and compared with that in the layered media. The results show that whether the stiffness profiles are smoothly varying or layered, the fundamental mode dominates the surface wave field and the effective phase velocity approaches to the phase velocity of the mode in far field for the regular profiles. For the irregular profiles, the higher modes have a significant influence on the surface wave field. The intensity and the frequency range of the influence are related to variation of the profile stiffness. In media with smoothly varying stiffness, the tendency of the effective phase velocity of mode at high frequencies is above Rayleigh wave velocity of the medium with the smallest shear velocity; and the tendency of the phase velocity at high frequencies deviates from Rayleigh wave velocity of the surface medium. These characteristics are different between the layered media and the media with smoothly varying stiffness. The results show that when a medium with smoothly varying stiffnesses is modelled with a layered medium in the back-analysis of the measured dispersion data, the match between the measured and the theortical dispersion data and the calculated stiffness profile are influenced by number of layers.