Review of test methods for the micro-pore characteristics of soils

Microstructure and pore characteristics of soil determine its physical and mechanical properties such as deformation, strength, and permeability. The accurate characterization of soil microstructure is a crucial prerequisite for understanding soil texture and for the effective characterization of soil properties. This study aimed to evaluate the applicability and limitations of various soil micro-test methods, compare the resolution of different micro-test techniques, and present their results. Several different techniques and methods have been used to analyze soil micropore structures. In terms of micro-visualization, scanning electron microscopy (SEM) and computed tomography (CT) are common imaging methods that can present the microstructure of the soil surface and its interior through optical means. In addition, some methods, such as soil–water retention curve (SWRC), mercury intrusion porosimetry (MIP), gas adsorption (GA), and nuclear magnetic resonance (NMR,) indirectly assess the size-related information of soil pores through the pore characteristics of porous media. The targeted joint application may be selected according to varying objectives—MIP is used to obtain the main structure when studying the overall internal pores, supplemented by CT for three-dimensional remodeling; NMR is used when studying local pore damage to reflect the evolution of pore characteristics related to water storage, supplemented by SEM to support observations of surface or morphological structure damage. Finally, the direction for future development is to process the test results and transform the existing technical equipment.