*4.1. Scanning Electron Microscope Imaging*

To investigate the microstructural evolution mechanism of the effect of different cementation liquid content on the soil-water characteristics of expansive soils under the same bacterial liquid content conditions. The TESCAN MIRA4 field emission scanning electron microscope was used to image and analyze the expansive soils before and after modification by the MICP method to investigate the changes in particle morphology and porous structure. The sample is an irregular sphere less than 1 cm in diameter and the sample was dried before the test. The surface of the sample is identified as the test surface, which is sprayed with gold to enhance conductivity. Secondary electron imaging was performed using a scanning electron microscope with an electron energy of 10 kev and a magnification of 5 kx.
