【摘要】：工程場地剪切波速度結構是場地分類的重要參數(shù),在國際上多用30米深度內的平均剪切波速(Vs30)作為場地分類標準,國內以覆蓋土層厚度和20米深度內的等效剪切波速作為場地分類標準。土層的剪切波速度結構也是進行場地地震反應分析計算中的必須參數(shù)。因此,在工程勘察中剪切波速度結構的測試尤為重要。目前,對場地剪切波速的勘察主要有鉆孔直接測試法和面波測試法,其中鉆孔法結果直觀、可靠,但經濟成本高,且是一種破壞性的勘察方法,不易大面積開展；面波法以其無損性、經濟快速的優(yōu)點,成為場地普查的一種快捷方法,在淺勘領域獲得廣泛應用。本文在回顧分層介質中面波的傳播理論、主動源和被動源面波淺勘方法(主要是基于微動信息的空間自相關技術,SPAC,SPatial AutoCorrelation;地震背景噪聲互相關成像技術,NCF, ambient Noise Correlation Function)的基礎上,基于SPAC和NCF物理基礎的一致性,提出將主動源面波淺勘,傳統(tǒng)的微動SPAC方法和NCF方法聯(lián)合用于小尺度面波淺勘領域,并嘗試將大尺度三維面波成像技術引入到小尺度面波勘探中,實現(xiàn)面波淺勘的三維成像。針對研究目的和設想,在云南省玉溪某地設計了一個直徑為16米,包含有23個垂直單分量檢波器的圓形臺陣,進行了主動源和被動源面波觀測的試驗研究。對于SPAC方法,設計了一種特殊點約束技術從空間自相關系數(shù)中提取頻散曲線的方法,并提取了6.7-23Hz頻段可靠的頻散曲線,通過對該觀測的頻散曲線與預測模型的頻散曲線進行擬合,反演得到S波速度結構,并與鉆孔測試結果吻合；對于NCF技術,通過互相關計算,獲得了不同路徑的時域互相關函數(shù),對質量較高的互相關函數(shù)提取了群速度頻散曲線,并獲得了不同路徑的頻散特征；對主動源記錄,采用表面波譜分析技術(SASW)獲得了不同路徑的頻散曲線；以SPAC的一維反演結果作為初始模型,對NCF和SASW獲得的頻散曲線進行了反演,得到了不同路徑,不同深度的S波速度結構,初步實現(xiàn)了面波淺勘的三維速度成像。
[Abstract]:The shear wave velocity structure is an important parameter in site classification. The average shear wave velocity (Vs30) in the depth of 30 meters is used as the standard of site classification in the world. In China, the equivalent shear wave velocity within 20 m depth and the thickness of overlying soil layer are taken as the site classification criteria. The shear wave velocity structure of soil layer is also a necessary parameter in the analysis and calculation of site seismic response. Therefore, it is very important to test the shear wave velocity structure in engineering survey. At present, the investigation of the shear wave velocity of the site mainly includes drilling direct testing method and surface wave testing method. The results of drilling method are intuitive and reliable, but the economic cost is high, and it is a destructive survey method, which is not easy to carry out in a large area. Because of its advantages of nondestructive and rapid economy, surface wave method has been widely used in the field of shallow prospecting. In this paper, the propagation theory of surface waves in layered media, the shallow prospecting methods of active and passive surface waves (mainly spatial autocorrelation based on fretting information, SPAC,SPatial AutoCorrelation;) are reviewed. Based on the seismic background noise cross-correlation imaging technique, NCF, ambient Noise Correlation Function) and the consistency of the physical basis of SPAC and NCF, it is proposed that the active source surface wave shallow prospecting, the traditional fretting SPAC method and the NCF method be used in the field of small scale surface wave shallow prospecting. The large scale 3D surface wave imaging technology is introduced into the small scale surface wave exploration to realize the 3D imaging of surface wave shallow prospecting. A circular array with a diameter of 16 meters and 23 vertical single-component geophones was designed in a certain area of Yuxi Yunnan Province for the purpose and assumption of the research. The experimental study of active and passive source surface wave observation was carried out. For the SPAC method, a special point constraint technique is designed to extract the dispersion curve from the spatial autocorrelation coefficient, and the reliable dispersion curve in the 6.7-23Hz band is extracted. By fitting the observed dispersion curve with the dispersion curve of the prediction model, the S-wave velocity structure is obtained by inversion, and the results are in good agreement with the borehole test results. For NCF technology, the time-domain cross-correlation function of different paths is obtained by cross-correlation calculation, and the dispersion curve of group velocity is extracted for the high-quality cross-correlation function, and the dispersion characteristics of different paths are obtained. For active source records, the dispersion curves of different paths are obtained by surface spectrum analysis (SASW). Using the one-dimensional inversion results of SPAC as the initial model, the dispersion curves obtained by NCF and SASW are inversed. The S-wave velocity structures with different paths and depths are obtained, and the 3-D velocity imaging of shallow surface waves is preliminarily realized.
【學位授予單位】：中國地震局地球物理研究所
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P631.4

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本文編號：2341780