【作者】 杨刚；

【导师】 师黎静；

【作者基本信息】 中国地震局工程力学研究所 ， 防灾减灾工程及防护工程， 2012， 硕士

【摘要】 瑞利波频散特性是瑞利波勘察法的理论基础。介质中的倾斜分界面对瑞利波的传播有着重要影响。研究包含倾斜分界面介质中的瑞利波频散特性，可以拓展瑞利波法在此类复杂介质中的应用，对丰富瑞利波传播理论和场地勘察手段有着重要的理论意义和应用价值。本文利用FLAC3D建立了双层介质动力模型，数值模拟了稳态瑞利波方法的激振、数据采集和分析过程，提取了瑞利波频散曲线，重点研究了包含倾斜分界面的介质中瑞利波频散特性。完成的主要工作和取得的成果如下：1、利用FLAC3D建立了水平双层层状介质动力模型，对稳态瑞利波法进行了模拟。结果表明，采用互相关法提取的频散曲线与理论计算值非常接近；且间距相同、不同位置观测点对提取的频散曲线没有明显差别，验证了水平成层介质中瑞利波频散曲线与观测点的位置无关这一基本特征。说明了利用FLAC3D进行稳态瑞利波法数值模拟可行，精度满足要求。2、建立了5%、10%和15%的3个不同倾斜坡度分界面的双层层状介质动力模型。通过上坡向稳态激振，下坡向记录，每个模型提取了23对观测点对应的瑞利波频散曲线，研究了包含倾斜分界面介质中的瑞利波频散曲线特性。3、研究表明，倾斜分界面对瑞利波的频散特性有着重要影响，测试的频散曲线与两观测点中间位置、浅端观测点和深端观测点对应剖面的理论计算值均有很大差别，偏离程度远大于两观测点土层厚度差别引起的扰动，并且随着坡度的增大而增大。4、分析指出，位于倾斜分界面不同位置处，即使间距相等的观测点，提取的频散曲线也不同；在包含倾斜分界面的介质中，稳态瑞利波法提取的频散曲线还与观测点相对倾斜分界面的位置有关。5、探讨了通过修正观测分析结果，来获得倾斜分界面介质中观测点下平均速度结构的途径。最后，提出了进一步研究展望。更多还原

【Abstract】 Dispersion characteristic is the theoretical basis of Rayleigh wavedetection method. The presence of dipping layer has significant influence onthe Rayleigh wave propagation. Researches on the dispersion characteristic onsites with dipping layer can expand the application of the Rayleigh wavemethod to those complex sites, and have important theoretical significanceand application value on the propagation theory and reconnaissance means ofRayleigh wave.In this paper, FLAC3D is used to set up dynamic models of double layer,the data acquisition and analysis process of Steady-state Rayleigh method aresimulated, and dispersion curves of Rayleigh wave are extracted. Studies arefocused on the dispersion characteristic of Rayleigh wave in the medium withdipping layer. The main results and accomplishments are as follows:1. Flat double-layer models are setup and the steady-state Rayleigh wavetest is simulated by FLAC3D. The dispersion curves obtained by crosscorrelation method are close to the theoretical value, and there is nosignificant difference between the dispersion curves observed at differentlocation but with same span, which verifies that the Rayleigh dispersioncurves in flat-layered medium are irrelevant to the observation location. So itis applicable and accurate enough to simulate steady-state Rayleigh wave testby FLAC3D.2. Three double-layered models with different dipping slopes of5%,10%and15%are setup. The test and analysis of steady-state Rayleigh wavemethod excited at uphill and recorded at downhill are simulated. Dispersioncurves corresponding to23pairs of observation locations are extracted, andthe dispersion characteristic of Rayleigh wave is studied.3. Study on the models with dipping layer shows that the presence ofdipping layer has significant influence on the Rayleigh wave dispersioncharacteristic, the observed dispersion curves are different from the theoreticalones in centre position, shallow observation point or deep observation point.The deviations are much bigger than those caused only by the difference ofthe thickness below the two observation stations, and the deviations increasewith the increase of dipping slpoes.4. Analysis also shows that even with the same observation spacing,dispersion curves also alternated at different locations relative to the dippinglayer, indicating that the extracted dispersion curves of Rayleigh wave arerelevant to observation locations.5. It is discussed that the way to obtain the average velocity of dippinglayer sites under observation stations by correcting the results of the observation and analysis. Finally, further researches are also suggested.更多还原