Investigation of freeze-thaw damage mechanism of dispersed saline soils considering water-salt transport
To investigate the freezing-salt expansion damage mechanism of soil during the freezing and thawing cycle process,freezing temperature tests and scanning electron microscopy(SEM)were combined to analyze how different numbers of freezing and thawing cycles,types of salts,and water content affect the soil's structure and properties.Freezing temperature change curves under varying cycle times and SEM electron microscope images of frozen soil at different water content levels were obtained.Drawing from classical heat transfer theory and water-salt transport equations,a numerical model was established to simulate water-salt transport during freeze-thaw cycles.On this basis,combined with experimental work,the failure mechanism of soil during water and salt transport process was analyzed and studied.The results show that the freezing process in the study area experiences a constant and decreasing stage due to soil body dispersion.As the number of freeze-thaw cycles increases,the soil body's freezing temperature initially rises and then stabilizes at a certain temperature.This is related to changes in soil particle size,particle arrangement,and gradual penetration of internal microcracks during freeze-thaw cycles.The migration of water salts in the soil during freeze-thaw cycles is the primary factor influencing soil strength.Water-salt migration occurs due to temperature and solute gradients,leading to changes in soil strength and structure.Sodium sulfate has a more pronounced impact on soil structure changes during freezing and thawing compared to sodium bicarbonate.Specifically,sodium sulfate crystals expand by a volume of 3.18 times during freeze-thaw cycles,resulting in soil expansion after the cycles,which alters the soil structure.This research contributes to understanding the freeze-thaw damage mechanism in salt-containing permafrost projects within seasonal permafrost areas.6 tabs,13 figs,32 refs.
NETL
NSTL
万方数据
