Abstract: Soil is one of the most basic engineering materials, but the nature of soil is often difficult to meet the needs of engineering. In recent years, due to the advantages of wide application range and easy improvement of strength after soil solidification/stabilization (S/S technology), solidified soil has been widely concerned and applied. The process of solidifying soil involves complicated physical and chemical reactions. In order to recognize the solidification mechanism, evaluate the solidification effect and obtain improvement measures, it is necessary to perfect the microscopic method of studying solidified soil and establish the corresponding testing and evaluation system. At present, the microscopic evaluation of solidified soil mainly focuses on the analysis of material composition and microstructure two parts. The corresponding testing methods mainly include X-ray diffraction analysis (XRD), scanning electron microscope-energy spectrum analysis system (SEM/EDX), electronic computed tomography (CT), mercury intrusion method (MIP), resistivity method, nuclear magnetic resonance (NMR) and other technologies. However, there are still some problems in the application of these mainstream testing methods to the microscopic evaluation of solidified soil. These disadvantages may be caused by immature technology, or due to unclear understanding of the relationship between testing principle and curing mechanism, or may be inherent disadvantages of the method itself. Therefore, there is still a broad space for improvement, exploration and development of current mainstream testing methods. Potential information contained in XRD can be obtained through reasonable experimental design, and quantitative problems can be solved. Through the analysis of SEM data and the cooperation with other technologies, the micro-three-dimensional morphology of solidified soil and the material information of micro-regions in the image can be mastered to a certain extent. Through the improvement of CT technology, three-dimensional reconstruction of solidified soil microstructure and evaluation of solidification effect can be realized without damage. Through optimization of MIP sample making process and improvement of model equation, problems such as "bottleneck hole" and "shielding hole" can be avoided to a certain extent, and test error can be reduced. Through continuous optimization of resistivity method, it can realize fast, nondestructive and conti-nuous large-area site evaluation of solidified soil. Through the study of NMR testing process and inversion process, it will help to improve the detection accuracy and reduce the sample requirements. In this paper, the microscopic testing methods commonly used in the research of solidified soil are summarized, the common problems of these methods in the research of solidified soil are analyzed emphatically, and the main improvement measures at present are summarized. It is pointed out that an accurate understanding of the mechanism of the method is the basis of application, and the development direction and research mode of micro-research on solidified soil in the future are put forward, so as to provide reference for micro-test research on solidified soil.
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