本文選題：瑞利面波 + 波場數(shù)值模擬��； 參考：《西南交通大學(xué)》2017年碩士論文

【摘要】：瑞利面波廣泛的被用于工程質(zhì)量檢測和工程勘察領(lǐng)域,得益于它的速度與橫波速度相近且具有頻散的運(yùn)動(dòng)學(xué)特性,除此之外瑞利面波還具有橢圓極化的動(dòng)力學(xué)特性,它與速度頻散具有一定的相似性,都會(huì)隨著介質(zhì)的變化而變化。瑞利面波在均勻半空間中速度頻散和橢圓極化頻散研究已經(jīng)取得了一定成果,但起伏地形下瑞利面波的速度頻散研究相對較少,相比之下橢圓極化頻散則少之更少。本論文采用數(shù)值模擬的方法,針對起伏地形進(jìn)行地震波場數(shù)值模擬,進(jìn)而對速度頻散和橢圓極化頻散分析,本文主要從以下三個(gè)方面著手:1.以地震波傳播理論為基礎(chǔ)展開瑞利面波速度頻散和橢圓極化頻散的論述,對瑞利面波速度頻散和橢圓極化率頻散的提取方法進(jìn)行了相關(guān)闡述。2.建立均勻半空間模型考察瑞利面波波場傳播特征,驗(yàn)證理論分析結(jié)果的正確性與數(shù)值模擬方法的合理性,進(jìn)而展開起伏地形條件下地震波的波場模擬,考察地形隆起高度和凹陷深度對瑞利面波速度頻散和橢圓極化率頻散的影響。3.建立存在局部異常體空洞的隆起和凹陷地形數(shù)值模型,分析該條件下地震波波場傳播特征,與單純地形數(shù)值模型作比較,深入研究局部異常體的存在對瑞利面波速度頻散和橢圓極化率頻散的影響。通過以上研究,取得了以下主要研究成果:1.與均勻半空間模型相比,單純地形條件下數(shù)值模型的地震波波場較為復(fù)雜,不僅有震源激發(fā)時(shí)產(chǎn)生的體波和面波,還有地形效應(yīng)產(chǎn)生的轉(zhuǎn)波。由于地形效應(yīng)的作用還會(huì)導(dǎo)致瑞利面波出現(xiàn)速度頻散,具體表現(xiàn)為隆起地形的近源端區(qū)域瑞利面波速度降低而遠(yuǎn)源端區(qū)域速度增加,當(dāng)為凹陷地形時(shí)則相反。并且這種變化趨勢隨著起伏程度的增加變得愈加明顯。類似的地形效應(yīng)還會(huì)導(dǎo)致瑞利面波出現(xiàn)橢圓極化率頻散,具體表現(xiàn)如下:當(dāng)為隆起地形時(shí)近源端區(qū)域瑞利面波橢圓極化率值變大而遠(yuǎn)源端區(qū)域變小,當(dāng)為凹陷地形時(shí)則相反,并且隨著地形起伏程度增加這種異常趨勢變的愈加明顯。2.對于存在局部異常體的地形模型而言,與單純地形數(shù)值模型地震波波場具有一定的相似性,但也有區(qū)別,具體表現(xiàn)在地震波的傳播不僅受到地形效應(yīng)的影響還要受異常體的干擾,當(dāng)?shù)卣鸩ń?jīng)過異常體時(shí),異常體相當(dāng)于一個(gè)震源會(huì)引起波場的轉(zhuǎn)換,經(jīng)對比研究發(fā)現(xiàn),地形效應(yīng)對瑞利面波速度頻散和橢圓極化率頻散的影響更為深刻,局部異常體只是在其周圍區(qū)域加深了這種頻散效應(yīng)。通過本論文的研究深化了瑞利面波在起伏地形條件下波場傳播的認(rèn)識(shí),強(qiáng)化了對瑞利面波速度頻散與橢圓極化率頻散的認(rèn)知,完善了瑞利面波在起伏地形中探測方面的理論基礎(chǔ),對于完善學(xué)科理論,促進(jìn)學(xué)科發(fā)展,具有極大的幫助。
[Abstract]:Rayleigh surface wave is widely used in engineering quality detection and engineering investigation, because its velocity is close to that of shear wave and has the characteristic of dispersion kinematics. In addition, Rayleigh surface wave also has the dynamic characteristics of elliptical polarization.It is similar to the velocity dispersion and will change with the change of the medium.Some achievements have been made in the study of Rayleigh surface wave velocity dispersion and elliptical polarization dispersion in uniform half-space, but the velocity dispersion of Rayleigh surface wave in undulating terrain is less than that of elliptical polarization dispersion.In this paper, the numerical simulation method is used to simulate the seismic wave field of the undulating terrain, and then the velocity dispersion and elliptical polarization dispersion are analyzed. In this paper, the following three aspects are discussed: 1.Based on seismic wave propagation theory, Rayleigh wave velocity dispersion and elliptical polarization dispersion are discussed, and the extraction methods of Rayleigh wave velocity dispersion and elliptical polarizability dispersion are expounded.A uniform half-space model is established to investigate the propagation characteristics of Rayleigh surface wave field. The correctness of the theoretical analysis results and the rationality of the numerical simulation method are verified, and the wave field simulation of seismic waves under undulating topography is carried out.The effects of height of terrain uplift and depth of depression on Rayleigh wave velocity dispersion and elliptical polarizability dispersion are investigated.The topographic numerical models of uplift and depression with local anomalous voids are established, and the propagation characteristics of seismic wave field under these conditions are analyzed and compared with the simple topographic numerical model.The influence of the existence of local anomalous bodies on Rayleigh wave velocity dispersion and elliptical polarizability dispersion is studied.Through the above research, we have obtained the following main research results: 1. 1.Compared with the homogeneous half-space model, the seismic wave field of the numerical model under the simple terrain condition is more complex, not only the body wave and the surface wave generated by the source excitation, but also the rotational wave generated by the topographic effect.Because of the effect of topographic effect, Rayleigh surface wave will appear velocity dispersion, which is represented by the decrease of Rayleigh wave velocity in near source region of uplift terrain and the increase of far source wave velocity, but the contrary when it is concave terrain.And the trend becomes more obvious as the degree of fluctuation increases.Similar topographic effects also lead to elliptical polarizability dispersion of Rayleigh surface waves, which is shown as follows: the elliptical polarizability of Rayleigh surface waves near the source end becomes larger while that of the distant source ends becomes smaller when the topography is uplift, and the opposite is true for the concave terrain.And with the increase of topographic fluctuation, this abnormal trend becomes more obvious. 2. 2.For the topographic model with local anomalous body, it is similar to the seismic wave field of the simple topographic numerical model, but it is also different from that of the simple topographic numerical model.The concrete manifestation is that the propagation of seismic wave is not only affected by topographic effect but also disturbed by abnormal body. When the seismic wave passes through the abnormal body, the anomalous body is equivalent to a source and will cause wave field conversion.The effect of topography on Rayleigh wave velocity dispersion and elliptical polarizability dispersion is more profound, and the local anomalous body only deepens the dispersion effect in the surrounding region.Through the research in this paper, we deepen the understanding of Rayleigh surface wave propagation in undulating terrain, and strengthen the understanding of Rayleigh wave velocity dispersion and elliptical polarizability dispersion.The theoretical basis of Rayleigh wave detection in undulating terrain is improved, which is of great help to the improvement of discipline theory and the development of subject.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU195

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