【摘要】：原狀網(wǎng)紋紅土同重塑網(wǎng)紋紅土的宏觀力學(xué)特性存在差異,而土體宏觀力學(xué)特性由其微觀結(jié)構(gòu)決定。為從微觀角度深入揭示原狀和重塑網(wǎng)紋紅土力學(xué)特性差異,本文基于室內(nèi)擊實(shí)試驗(yàn)和SEM-EDS試驗(yàn)及數(shù)字圖像處理技術(shù),以對(duì)他們的微結(jié)構(gòu)進(jìn)行定量對(duì)比分析,分析了不同放大倍數(shù)和不同閾值選取對(duì)有效閾值區(qū)間內(nèi)三維孔隙率計(jì)算結(jié)果的影響,并探討了平均接觸面積率與宏觀孔隙率之間的關(guān)系。通過(guò)研究得出如下主要結(jié)論:(1)基于重塑網(wǎng)紋紅土SEM試驗(yàn)結(jié)果和數(shù)字圖像處理技術(shù),構(gòu)建了以像素面積為底面、閾值范圍為高度的有效閾值區(qū)間內(nèi)三維孔隙率計(jì)算模型,并實(shí)際應(yīng)用于不同試驗(yàn)條件下的SEM圖像孔隙數(shù)量、面積及孔隙率演變分析,與平面孔隙率方法結(jié)果對(duì)比表明三維孔隙率計(jì)算結(jié)果更符合土體孔隙實(shí)際分布情況。(2)重塑網(wǎng)紋紅土微觀孔隙率定量結(jié)果表明,由SEM圖像計(jì)算獲得的三維孔隙率大都大于宏觀孔隙率,2000倍下SEM計(jì)算結(jié)果更接近宏觀孔隙率,同時(shí)發(fā)現(xiàn)閾值選取是定量分析的關(guān)鍵點(diǎn),基于平均閾值獲得的三維孔隙率結(jié)果偏差比選取最終閾值獲得的結(jié)果要小得多。平均接觸面積率分析表明,試樣計(jì)算所得平均接觸面積率大概在3%以下,并結(jié)合網(wǎng)紋紅土粘土礦物結(jié)合水膜厚度300?特點(diǎn),擬合得到平均接觸面積率與宏觀孔隙率之間的冪函數(shù)關(guān)系。(3)原狀網(wǎng)紋紅土微結(jié)構(gòu)研究結(jié)果表明,紅色基質(zhì)中土顆粒排列緊密,孔隙率較小且孔隙之間的連通性較差,土顆粒表面比較粗糙;白色網(wǎng)紋中孔隙率大且孔隙數(shù)量多,顆粒多表現(xiàn)為光滑的片狀結(jié)構(gòu),主要以面面接觸為主。定量分析結(jié)果表明紅色基質(zhì)的計(jì)算三維孔隙率均值為0.371,白色網(wǎng)紋的計(jì)算三維孔隙率均值為0.450。(4)EDS試驗(yàn)分析結(jié)果表明紅色基質(zhì)和白色網(wǎng)紋中的主要化學(xué)元素為氧、硅、鋁和碳,及少量的鉀和鎂。其中鐵元素流失是造成白色網(wǎng)紋和紅色基質(zhì)色彩差別的主要原因,且鐵元素有富集現(xiàn)象。碳元素為網(wǎng)紋紅土中因有機(jī)酸形成酸性還原環(huán)境導(dǎo)致鐵元素的遷移的觀點(diǎn)提供了一定依據(jù)。
[Abstract]:The macroscopic mechanical properties of undisturbed reticulated red soil are different from those of remolded reticulated red soil, but the macroscopic mechanical properties of soil are determined by its microstructure. In order to reveal the difference of mechanical properties between the original and reconstructed reticulated red soil from the microscopic angle, this paper makes a quantitative comparative analysis of their microstructure based on the laboratory compaction test, SEM-EDS test and digital image processing technology. The influence of different magnification and different threshold on the calculation results of 3D porosity in the effective threshold range is analyzed, and the relationship between the average contact area rate and the macroscopic porosity is discussed. The main conclusions are as follows: (1) based on the SEM test results of remolded reticulated laterite and digital image processing technology, a three-dimensional porosity calculation model with pixel area as the bottom and threshold range as the height is constructed. And it is applied to analyze the evolution of porosity, area and porosity in SEM images under different experimental conditions. The comparison of the results with the plane porosity method shows that the three-dimensional porosity calculation results are more in line with the actual distribution of soil porosity. (2) the quantitative results of microscopic porosity of remolded reticulated red soil show that, The 3D porosity calculated by SEM image is mostly larger than that of macro porosity by 2000 times. The results of SEM calculation are closer to macroscopic porosity. At the same time, it is found that the selection of threshold is the key point of quantitative analysis. The deviation of 3D porosity based on the average threshold is much smaller than that obtained by selecting the final threshold. The analysis of average contact area ratio shows that the average contact area rate calculated by the sample is about 3%, and the thickness of water film is 300? The power function relationship between average contact area ratio and macroscopic porosity was obtained by fitting. (3) the results of microstructural study of undisturbed reticulated laterite show that the soil particles in red matrix are closely arranged, the porosity is small and the connectivity between pores is poor. The surface of soil particles is rough, the porosity of white mesh is large and the number of pores is large, and most of the particles are smooth flake structure, mainly surface contact. The results of quantitative analysis show that the calculated three-dimensional porosity of red matrix is 0.371, and that of white mesh is 0.450. (4) the results of EDS test show that the main chemical elements in red matrix and white mesh are oxygen, silicon, aluminum and carbon. And a small amount of potassium and magnesium. The loss of iron is the main reason for the color difference between white mesh and red matrix. The carbon element provides a certain basis for the viewpoint that the organic acid forms an acid reduction environment in the reticulated red soil, which leads to the migration of iron elements.
【學(xué)位授予單位】：合肥工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TU446

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