砂土微观结构样品制备技术及量化方法研究

土体的微观结构是决定其工程特性的重要内在因素，但对于砂土而言，如何制备适合微观分析的样品以及快速准确量化结构参数一直面临诸多挑战。为此，提出一种真空冷冻干燥?注胶相结合的砂土样品制备技术，该技术可在有效去除土样水分的同时保持样品原状结构不被扰动，并可用于后续加工处理。针对不同粒度的砂土样品，分别使用扫描电子显微镜和光学显微镜对制备的试样进行观察，基于自主研发的土体微观结构定量分析系统SMAS对拍摄的照片进行精细量化分析，提出了由土颗粒数量、颗粒周长、表观孔隙率、形状系数、等效直径、分形维数和形态比等参数构成的量度指标体系对砂土样品微观结构特征进行定量评价。研究结果表明：提出的真空冷冻干燥?注胶相结合的砂土样品制备技术具有操作简单、稳定可靠等特点，能有效维持砂土的原状结构；比较而言，扫描电镜更适用于粉细砂的微观结构分析，而光学显微镜更适用于中粗砂的微观结构分析；SMAS能有效识别微观结构图像中的土颗粒及孔隙，为定量分析砂土或其他土体的微观结构特征提供了高效的工具。

Sample preparation technique and microstructure quantification method for sandy soil

The microstructure of soil is an important internal factor that determines its engineering properties. However, preparing suitable samples for microstructure analysis and quantifying structural parameters have always been challenging. A method of vacuum freeze drying-glue injection for preparing sandy soil samples is introduced. This method can remove water and maintain the samples’ original structure for further processing. A series of sample images with different grain sizes were taken by SEM and optical microscope, respectively. Based on the self-developed soil microstructure quantitative analysis system SMAS, the images were quantitatively analyzed. A quantitative index system composed of soil particle number, particle perimeter, apparent porosity, shape factor, equivalent diameter, fractal dimension and shape ratio were proposed and used to quantitatively evaluate the microstructure characteristics of sand soil samples. The results show that the vacuum freeze drying-glue injection method for preparing samples has the advantages of convenient operation and reliable results, which can effectively maintain original structured sand. In comparison, SEM is more suitable for the microstructure analysis of fine sand, while optical microscopy is more suitable for medium/coarse sand. SMAS can effectively identify soil particles and pores in microstructure images, providing an efficient tool for quantitative analysis of the microstructure characteristics of sand or other soils.