本文關(guān)鍵詞： 噪聲源 瑞利面波 頻散曲線 粘性邊界 數(shù)值模擬　出處：《西南交通大學(xué)》2015年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：隨著大量工程應(yīng)用深入地質(zhì)條件復(fù)雜地區(qū),工程施工越發(fā)依賴(lài)全面的地質(zhì)信息資料。為了給工程施工提供信息化保障,地球物理科學(xué)及物探技術(shù)在工程領(lǐng)域快速發(fā)展。利用噪聲源瑞利面波的波場(chǎng)特性進(jìn)行探測(cè)的實(shí)際應(yīng)用已在國(guó)內(nèi)外地震、工程勘探等領(lǐng)域展開(kāi),而對(duì)噪聲源瑞利面波波場(chǎng)的理論研究還相對(duì)較少。由于噪聲源的隨機(jī)維度多、模擬難度大,噪聲源瑞利面波波場(chǎng)的研究主要集中在現(xiàn)場(chǎng)試驗(yàn),數(shù)值模擬研究發(fā)展較慢。本文基于波動(dòng)理論及瑞利面波的頻散曲線特性,利用Ansys有限元軟件,采用Plane182四角點(diǎn)平面單元建立了簡(jiǎn)化的噪聲源數(shù)值模型空間,并使用Combine14彈簧單元完善了模型邊界條件,形成粘性邊界。最后,使用Geogia Seismic Pro數(shù)據(jù)處理軟件,利用噪聲源F-K與SPAC法提取頻散曲線,展開(kāi)了噪聲源瑞利面波在均勻介質(zhì)及非均勻介質(zhì)條件下的波場(chǎng)數(shù)值模擬及分析,得到了以下結(jié)論：在均勻介質(zhì)中,展開(kāi)了同側(cè)源、異側(cè)源兩種噪聲源簡(jiǎn)化模擬模型,實(shí)驗(yàn)發(fā)現(xiàn)噪聲源F-K法和SPAC法能有效提取同側(cè)源和異側(cè)源瑞利面波的頻散曲線,達(dá)到了較好的探測(cè)效果。此外,利用均勻介質(zhì)本文開(kāi)展了近場(chǎng)干擾和假頻干擾分析研究。研究發(fā)現(xiàn)在近場(chǎng)區(qū)瑞利面波的波速向體波波速偏移,當(dāng)體波與面波的到時(shí)相差一個(gè)雷克子波時(shí)長(zhǎng),體波與面波完全分離,近場(chǎng)干擾現(xiàn)象消失。在提取頻散曲線時(shí)出現(xiàn)空間域假頻干擾,這種干擾在主動(dòng)源和噪聲源中均存在。主動(dòng)源信號(hào)在奈奎斯特頻率外出現(xiàn)同向假頻信號(hào),噪聲源除含有同向假頻信號(hào)外還具有逆向的假頻分量,影響頻散曲線的提取。通過(guò)提高空間采樣率能在波數(shù)域增大真實(shí)信號(hào)與假頻信號(hào)的區(qū)分度,壓制假頻信號(hào)的存在區(qū)間,能有效壓制空間假頻信號(hào)。在非均勻介質(zhì)中,本文分別建立了矩形空洞、矩形高速層、圓形低速體三種異常體的非均勻介質(zhì),通過(guò)數(shù)值模擬研究噪聲源瑞利面波頻散特性對(duì)其的分辨及適用情況。研究發(fā)現(xiàn),噪聲源對(duì)矩形異常體的分辨能力較好,可以判斷異常體的中心位置,但異常體邊界呈現(xiàn)速度過(guò)渡段,無(wú)法準(zhǔn)確判斷異常體邊界位置。在圓形低速異常體的研究中,噪聲源瑞利面波頻散所繪制速度剖面相較矩形異常體的誤差較大,對(duì)圓形異常體無(wú)法準(zhǔn)確定位,且無(wú)法判斷圓形異常體的底部邊界,但依然可以判斷速度變化趨勢(shì),輔助少量取芯鉆孔,依然可以取得較好的預(yù)報(bào)效果。
[Abstract]:With a large number of engineering applications going deep into complex geological areas, engineering construction relies more and more on comprehensive geological information materials. In order to provide information support for engineering construction, Geophysical science and geophysical exploration technology have developed rapidly in the engineering field. The practical application of Rayleigh wave characteristics of noise source to the detection has been carried out in the fields of earthquake and engineering exploration at home and abroad. But the theoretical study of Rayleigh surface wave field of noise source is relatively few. Because of the random dimension of noise source and the difficulty of simulation, the research of Rayleigh surface wave field of noise source is mainly focused on the field test. Based on the wave theory and the dispersion curve characteristics of Rayleigh surface waves, a simplified numerical model space of noise source is established by using Ansys finite element software and Plane182 quadrilateral plane element. Combine14 spring element is used to perfect the boundary condition of the model to form viscous boundary. Finally, using Geogia Seismic Pro data processing software, the dispersion curve is extracted by using F-K and SPAC method of noise source. The numerical simulation and analysis of Rayleigh surface waves of noise sources in homogeneous and non-uniform media are carried out. The following conclusions are obtained: in homogeneous media, two simplified simulation models of the same side source and different side source are developed. The experimental results show that the noise source F-K method and SPAC method can effectively extract the dispersion curves of Rayleigh surface waves from the same side source and the other side source, and achieve a good detection effect. In this paper, the near field interference and false frequency interference are studied in homogeneous medium. It is found that the velocities of Rayleigh surface waves in the near field are shifted to body wave velocities, and when the arrival time of bulk wave and surface wave is one different from that of surface wave, the length of Rayleigh wavelet is one. Body wave and surface wave are separated completely, and near-field interference disappears. There is spatial false frequency interference in the extraction of dispersion curve, which exists in active source and noise source. The active source signal appears codirectional false frequency signal outside Nyquist frequency. The noise source not only contains the codirectional false frequency signal, but also has the reverse false frequency component, which affects the extraction of the dispersion curve. By increasing the spatial sampling rate, the division between the real signal and the false frequency signal can be increased in the wavenumber domain, and the existence interval of the false frequency signal can be suppressed. In this paper, three kinds of non-uniform media, rectangular cavity, rectangular high-speed layer and circular low velocity body, are established in non-uniform medium. The resolution and application of Rayleigh surface wave dispersion characteristics of noise source are studied by numerical simulation. It is found that the noise source has better resolution ability to rectangular abnormal body and can judge the center position of abnormal body. However, the boundary of abnormal body presents a velocity transition section, which can not accurately judge the position of abnormal body boundary. In the study of circular and low velocity abnormal body, the velocity profile drawn by Rayleigh wave dispersion of noise source is larger than that of rectangular anomalous body. It is impossible to locate the circular anomaly accurately and to judge the bottom boundary of the circular anomaly, but it is still possible to judge the trend of velocity change and to assist a small number of coring holes to achieve good prediction results.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：P631.4

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