Experimental study on unfrozen water and soil matric suction of the aeolian sand sampled from Tibet Plateau

Aeolian sand is sometimes used as geomaterial in cold regions of China. This paper tries to investigate the unfrozen water, matric suction of aeolian sand, which is related to its thermal and mechanical properties. The pF-meter matric suction sensor coupled with 5TM moisture content sensor that can operate in the subfreezing environment was used to measure the moisture content and matric suction of aeolian sand under different conditions. Combined with thermal resistor temperature probe, the relationship between unfrozen water and temperature is analyzed. The results indicate a significant phenomenon of latent heat absorption and release at freezing and thawing points. In addition, the phenomenon of the supercooling was observed with a value of -1.96 degrees C during stepwise temperature change. Most water in the sand freezes at freezing point 0 degrees C under rapid and stepwise temperature change. There is approximately 3% of unfrozen water content retained when the sand temperature drops to -15 degrees C. The soil matric suction increases very slowly at the stable freezing stage. These results provide the theoretical support for future research on the moisture migration mechanism and engineering application of aeolian sand in cold regions.