南水北调中线膨胀土/岩微观特征及其性质研究

对南水北调中线工程典型的强、中膨胀土/岩开展室内土工试验与X射线衍射试验，研究了其矿物成分及与胀缩性指标的关系，利用扫描电镜SEM图像进行了微观结构的定性分析，并基于MATLAB软件对孔隙和微结构单元体的微观特征进行了定量化研究，探讨了不同类型膨胀土/岩的颗粒形态、结构类型、裂隙分布等微观特征及其与工程特性的关系。结果表明：膨胀土/岩中的蒙脱石等黏土矿物含量高，强膨胀土/岩以絮凝结构，扁平状聚集体与卷曲片状颗粒为主，中膨胀土/岩以紊流状、粒状堆叠结构为主，片状聚集体与单粒体并存，前者微裂隙发育且定向性明显，孔隙比大，孔隙分形维数与颗粒尺寸小于后者。膨胀土/岩微结构单元圆形度低，复杂度高。膨胀岩定向排列特征显著，颗粒分形维数小，颗粒分形维数与膨胀潜势和孔隙比的变化规律一致。微观组分和结构特征与物性指标分别呈线性关系与负指数幂关系。

Microstructure and characteristics of expansive soil and rock of middle route of South-to-North Water Diversion Project

For typical strong and medium expansive soil and rock of the middle route of the South-to-North Water Diversion Project, mineral composition and its correlation with expansion and contraction indexes are studied through indoor soil tests and X-ray diffraction experiments. Qualitative analysis for microstructure is carried out by using the scanning electron microscopy images, and quantitative analysis for microstructures of pores and microstructural units is performed based on MATLAB. Microstructures such as particle morphology, structural type and microfracture distribution and their correlation with engineering characteristics are discussed. The results show that the content of clay minerals in expansive soil and rock is high. Strong expansive soil and rock have flocculation structure, flat aggregate and curly sheet-shape grains, and medium expansive soil and rock have turbulence and granular stack structure, flake aggregate and single grains. The former has higher void ratio, its microfracture with obvious orientation is well developed, and its pore fractal dimension and particle size are lower than those of the latter. The microstructural units of expansive soil and rock have low circular degree and high complexity. The orientation of expansion rock is significant and its particle fractal dimension is low. The fractal dimension has the same variation as the expansion potential and void ratio. The microcomposition, microstructure and physical properties exhibit linear and negative exponent correlations.