巴振宁, 严洋, 梁建文, 张艳菊. 基于TI介质模型的凸起地形对平面SH波的放大作用[J]. 工程力学, 2017, 34(8): 10-24. DOI: 10.6052/j.issn.1000-4750.2016.03.0197
引用本文: 巴振宁, 严洋, 梁建文, 张艳菊. 基于TI介质模型的凸起地形对平面SH波的放大作用[J]. 工程力学, 2017, 34(8): 10-24. DOI: 10.6052/j.issn.1000-4750.2016.03.0197
BA Zhen-ning, YAN Yang, LIANG Jian-wen, ZHANG Yan-ju. AMPLIFICATION OF PLANE SH WAVES BY A CONVEX TOPOGRAPHY BASED ON THE TI MEDIUM MODEL[J]. Engineering Mechanics, 2017, 34(8): 10-24. DOI: 10.6052/j.issn.1000-4750.2016.03.0197
Citation: BA Zhen-ning, YAN Yang, LIANG Jian-wen, ZHANG Yan-ju. AMPLIFICATION OF PLANE SH WAVES BY A CONVEX TOPOGRAPHY BASED ON THE TI MEDIUM MODEL[J]. Engineering Mechanics, 2017, 34(8): 10-24. DOI: 10.6052/j.issn.1000-4750.2016.03.0197

基于TI介质模型的凸起地形对平面SH波的放大作用

AMPLIFICATION OF PLANE SH WAVES BY A CONVEX TOPOGRAPHY BASED ON THE TI MEDIUM MODEL

  • 摘要: 在模拟地震波在介质中传播过程的研究中,正演模拟是一个重要的方面。该文采用间接边界元法(IBEM)对横观各向同性(TI)不同参数介质的凸起场地中入射SH波的散射问题进行了正演模拟,研究了TI凸起场地对SH波的放大效应。放大效应是通过地表位移与基岩露头位移幅值的比值来体现的。该间接边界元法结合了层状TI半空间精确动力刚度矩阵和均布斜线荷载动力格林函数,具有较高的精度。该文分别给出了TI介质凸起中SH波散射问题在频域和时域内的解答。频域内研究分析表明,土体TI介质参数的变化会对场地位移幅值的放大谱和空间分布产生显著的影响,即改变了凸起部分和土层的动力特性,使得两者动力相互作用发生改变。时域内研究表明,SH波在凸起周围的传播同时依赖于TI介质参数的具体取值和传播方向。时域位移幅值云图清晰地展示入射波、透射波、反射波和散射波的传播过程,凸起角点产生的散射波在TI介质中传播呈现"半椭圆"型,而在各向同性介质中呈现"半圆"型。

     

    Abstract: Forward modeling is an important method in simulation of seismic wave propagation in some medium. This paper adopts the indirect boundary element method (IBEM) to conduct the forward modeling to study the scattering problem of incident SH waves in transversely isotropic (TI) convex topography with various parameters, in order to give explicit interpretations to the amplification effect of this problem. The amplification effect is reflected by the ratio of the displacement amplitudes on the surface of the convex site and the bedrock outcrop. Combined with the precise dynamic matrix of layered TI half space and dynamic Green function of the site under evenly-distributed diagonal loads, the IBEM has much higher preciseness. The results of the incident SH waves scattering problem in a convex topography are provided in frequency and time domain respectively. Study in frequency domain implies that the amplification spectrum and spatial distribution of the displacement amplitudes are significantly affected by the soil TI properties, which indicates the change of TI medium parameters would cause fluctuations of the dynamics characteristics in both the convex part and the soil. Thus the dynamic interaction between them would change. Study in time domain shows that the propagation of SH wave around the convex topography depends on the values of TI medium parameters and propagation direction. Snapshots of instantaneous displacement amplitudes show the propagation process of incident waves, transmitted waves, reflection waves and scattered waves. The propagation of scattered waves generated at the convex corners is‘semi-elliptical’type in TI medium, but‘semi-circle’type in isotropic medium.

     

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