层状介质瑞利面波波场二维数值模拟研究

发布时间：2018-01-10 22:30

本文关键词：层状介质瑞利面波波场二维数值模拟研究　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：瑞利面波的速度频散早已在工程上获得了广泛的应用,而椭圆极化率频散虽然在场地卓越频率测试方面取得了一定的应用效果,但是在工程勘探领域的应用仍处于起始阶段,相关的正演数值模拟和理论研究仍不完备。深入展开水平层状介质瑞利面波波场传播特征的研究,对于该方法的发展和其理论的完善具有重要的工程价值和理论意义。论文采用数值模拟方法,针对水平层状介质,从速度频散与椭圆极化率频散两个方面展开系统的研究,主要包括以下几方面研究内容:(1)瑞利面波速度频散与椭圆极化率频散的基础理论研究。首先对瑞利面波的速度频散与椭圆极化率频散的解析计算方法展开详细论述,然后对瑞利面波频散分析中的傅里叶变换、F-K域变换分离波场、速度频散曲线的提取方法、椭圆极化率频散的提取方法等进行了相关论述。(2)均匀介质中瑞利面波速度频散和椭圆极化率频散的数值模拟研究。对于均匀半空间,分别使用点震源和平面波震源进行全波场数值模拟,结合理论研究结果,对波场传播特征进行观察与分析,验证理论分析结果的正确性与数值模拟方法的准确性。(3)水平层状介质中瑞利面波速度频散和椭圆极化率频散的数值模拟研究。选取低速覆盖和高速覆盖两种不同情况的二层水平层状介质,以及不同层厚与上层面波波长比值的数值模型,分别研究速度频散与椭圆极化率频散对水平分层介质的响应特征。(4)分层界面上的波型转换和能量分配分析。讨论面波在分层界面上发生的波型转换和能量分配,进而分析转换波对面波速度频散和椭圆极化率频散的影响。通过以上研究,主要取得以下研究成果:(1)对于水平二层介质并且覆盖层为低速介质的模型,由于分层界面发生面波与体波的转换,体波大部分能量传播至地表重新生成面波,对上层介质中波的传播影响较大,导致依据传统单一面波模式传播发展的速度频散和椭圆极化率频散分析方法的结果失真,但对速度频散的影响较小,对椭圆极化率频散的影响很大。(2)对于水平二层介质并且覆盖层为高速介质的模型,尽管分层界面仍发生面波与体波的转换,但体波大部分能量传播下层低速介质中,对上层介质中波的传播影响较小,对频散分析方法的结果影响不大。本论文的研究内容深化了瑞利面波在分层界面上与体波之间相互转换的认识,加强了对瑞利面波速度频散与椭圆极化率频散的理解,完善了瑞利面波在分层介质中探测方面的理论基础,为瑞利面波在工程中的应用提供更加完备的理论依据,对于完善该学科理论,促进学科发展,指导应用实践有极大帮助。
[Abstract]:Rayleigh wave velocity dispersion has been widely used in engineering, and the polarization ellipticity dispersion has certain application effect in the predominant frequency test, but the application in engineering exploration is still in the initial stage, numerical simulation and theoretical research related to forward further development is still incomplete. Horizontal layered medium Rayleigh wave field propagation characteristics, and has important practical value and theoretical significance for the development of this method and its theory. This paper using the method of numerical simulation for horizontal layered medium speed dispersion system research and the polarization ellipticity of the dispersion in two aspects, including the following research contents: (1) based on the theory of Rayleigh wave velocity dispersion dispersion and polarization ellipticity. First speed frequency of Rayleigh wave dispersion solution of dispersion and polarization ellipticity. A detailed discussion is presented, then the Rayleigh wave dispersion Fourier transform analysis, F-K transform domain wave field separation, extraction method of velocity dispersion curve, ellipse polarization dispersion extraction method was discussed. (2) Rayleigh surface wave in homogeneous medium velocity dispersion and numerical elliptical polarization the rate of dispersion simulation. For homogeneous half space, using point source and plane wave source full wave field numerical simulation, combined with the theoretical research results of wave propagation characteristics were observed and analyzed, and the accuracy of numerical simulation results verify the theoretical analysis. (3) Rayleigh in horizontal layered medium the surface wave velocity dispersion and polarization ellipticity of numerical dispersion simulation. Select two layer media coverage and low speed covering two different cases, and different layer thickness and the upper surface wave wavelength ratio numerical model Type of velocity dispersion respectively, the dispersion characteristics of the response of horizontal layered media and the polarization ellipticity. (4) analysis of wave type conversion and energy distribution on the interface layer. The discussion of surface wave mode conversion occurs in layered on the interface and energy distribution, and analysis of converted wave surface wave velocity dispersion and elliptical polarization the rate of dispersion effect. Through the above research, the main results are as following: (1) to the level of the two layer and covering layer for low medium model, due to the hierarchical interface of surface wave and body wave conversion, body wave spread to most of the energy surface to generate surface wave propagation effects on the upper, medium based on the traditional single lead to larger surface wave mode propagation development velocity dispersion and polarization ellipticity dispersion analysis method results in distortion, but less impact on dispersion, a great impact on the polarization ellipticity of dispersion for (2). The level of the two layer and covering layer for high speed medium model, although the layered interface still occurs surface wave and body wave conversion, but most of the lower body wave energy propagation medium low speed communication, has little influence on the upper medium, has little influence on the analysis method of dispersion results. Understanding the research contents of this thesis deepened Rayleigh wave in layered interface and bulk wave conversion between the strengthening of the Rayleigh wave velocity dispersion dispersion and polarization ellipticity of understanding, improve the detection theory of Rayleigh wave in layered media, and provide a theoretical basis for a more complete application of Rayleigh wave in engineering. For improving the scientific theory, promote the development of discipline, will be of great help to guide practical application.

【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU195

【参考文献】