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.