Evolution characteristics of microscopic pore structure of saline soil profile in Qian’an country, Northeastern China

摘要

The pore characteristics of saline soil greatly influence its engineering properties, such as deformation, strength, andpermeability. To explore the microscopic pore characteristics of the saline soil profile in Qian’an country, NortheasternChina, a study based on the mercury injection test (MIP) and the scanning electron microscope (SEM) test combined withfractal theory was carried out. The results reveal that the pore size of undisturbed saline soil at the sampling point presentsthe characteristic of trimodal distribution and shows different microscopic characteristics with a depth of 60 cm as theboundary. The shallow soil (surface-40 cm) has poor compactness, high porosity, and macropores (4-40 μm) dominate,while the deep soil (60-100 cm) has higher compactness, smaller porosity, and more uniform pore size distribution. Inaddition, the pore morphology of the saline soil profile is closer to the sub-long strip or oblate, which indicates the porehas a poor roundness, and the pore edge lines are relatively smooth. The geostatic stress, freeze-thaw cycle, clay content,and soluble salt affect the pore microstructure together. Furthermore, the pore characteristics were evaluated based onthe fractal dimension ( D ) and surface fractal dimension ( Dr ). D has the strongest correlation with the content of smallpores (0.04-0.4 μm), and Dr has the strongest correlation with the shape coefficient. D and Dr can jointly reflect themicroscopic pore structure characteristics with a good corresponding relationship.