小尺寸稳态瑞利波法试验的数值模拟

发布时间：2018-02-15 11:57

本文关键词： 瑞利波试验倾斜界面 Specfem2D　出处：《中国地震局工程力学研究所》2016年硕士论文　论文类型：学位论文

【摘要】：瑞利面波方法在地质勘测以及工程检验领域得到了广泛应用。虽然在实践中也大量用于经验性的勘测非均匀地质问题,但应用瑞利面波法对介质的水平以及倾斜界面的识别能力尚未有明确认识。研究瑞利波探测层状介质分界面的影响,对提高瑞利波法的精度和扩展其应用具有重要的意义。通过在简单易制备的场地模型上进行小尺寸稳态瑞利波试验,为研究这一问题提供了新思路。利用数值模拟方法,可以弥补现场试验受测试设备、测试环境、测试时间等限制而引起试验样本不足。对照数值模拟结果与现场试验结果,有利于更好总结相关特征和规律。本文利用谱元分析软件Specfem2D对不同场地上的小尺寸稳态瑞利面波试验进行了数值模拟,着重探讨了利用稳态瑞利波法识别成层场地水平和倾斜分界面的可行性。主要完成了的如下工作:1、分别利用Specfem2D软件对砂土和混凝土两类均匀场地上的小尺寸稳态瑞利波法试验进行了数值模拟。讨论了模型尺寸、网格大小以及计算时间步长等模型参数的选取,通过与理论解析解的对比,检验了数值模拟方法的可行性与精度;通过与现场测试结果对照,研究了不同道间距、偏移距对频散曲线的影响,为小尺寸瑞利波法现场测试提供了参考。2、数值模拟了水平双层场地上的小尺寸稳态瑞利波法试验。通过对比现场测试结果、数值模拟结果以及理论解析解,分析了低频段、高频段的相位差谱和频散曲线特征以及道间距对测试与模拟结果的影响。探讨了不同底层剪切波速下频散曲线首个“拐点”对应的瑞利波波长与分界面深度的关系,指出了在传统应用测试中通过降低激振频率、增加道间距以探测分界面做法的不足。3、介绍了倾斜界面双层场地上的小尺寸稳态瑞利波法试验,详细分析了不同测试方向、激振方向和道间距下获得的相位差谱特征;对其中道间距为0.5m的工况进行了数值模拟并细致分析。研究表明,在垂直于倾斜横截面方向测试可简化为水平成层场地;而在顺倾斜界面方向测试,浅端激振与深端激振下的结果存在明显差别,深端激振时的相位差整体上大于浅端激振下的相位差,可以据此来判别层状介质分界面是否倾斜,且相速度值相对较大的一侧其首层厚度较薄。
[Abstract]:Rayleigh surface wave method has been widely used in geological survey and engineering inspection. However, the Rayleigh wave method has not been used to recognize the horizontal and inclined interface of the medium. The effect of Rayleigh wave on the detection of layered media interface is studied. It is of great significance to improve the precision of Rayleigh wave method and to extend its application. A new idea is provided for the study of this problem by means of a small scale steady state Rayleigh wave test on a simple and easy preparation site model, and a numerical simulation method is used. It can make up for the shortage of test samples caused by the limitation of test equipment, test environment, test time and so on. In this paper, the spectral element analysis software Specfem2D is used to simulate the small scale steady Rayleigh wave test on different sites. The feasibility of using steady state Rayleigh wave method to identify horizontal and inclined boundary surfaces of layered site is emphatically discussed. The main work accomplished is as follows: 1. The small size steady state interface on two homogeneous sites of sand and concrete is obtained by using Specfem2D software. The numerical simulation of Rayleigh wave test is carried out. The model size is discussed. The feasibility and accuracy of the numerical simulation method are tested by comparing the mesh size and the calculation time step size with the theoretical analytical solution, and the different track spacing is studied by comparing with the field test results. The effect of offset on dispersion curve provides a reference for the field test of small size Rayleigh wave method. Numerical simulation of small size steady state Rayleigh wave test on horizontal bilayer site is carried out. The numerical simulation results and theoretical analytical solutions are used to analyze the low frequency band. The characteristics of phase difference spectrum and dispersion curve in high frequency band and the influence of channel spacing on the results of measurement and simulation are discussed. The relationship between Rayleigh wave length and the depth of interface between the first "inflection point" of the dispersion curve at different bottom shear wave velocities is discussed. This paper points out the deficiency of detecting the interface by decreasing the exciting frequency and increasing the channel spacing in the traditional test. The small size steady state Rayleigh wave test on the double layer site with inclined interface is introduced, and the different testing directions are analyzed in detail. The characteristics of phase difference spectrum obtained under excitation direction and channel spacing are numerically simulated and carefully analyzed in which the channel spacing is 0.5 m. The results show that the measurement in the direction perpendicular to the inclined cross section can be simplified as a horizontal stratified site. But in the direction test of inclined interface, the results of shallow end excitation and deep end excitation are obviously different. The phase difference of deep end excitation is larger than that of shallow end excitation, so we can judge whether the interface of layered medium is inclined or not. And the thickness of the first layer is thinner in the side where the phase velocity value is relatively large.
【学位授予单位】：中国地震局工程力学研究所
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P631.4

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