INVESTIGATION ON WATER RETENTION AND PERMEABILITY CHARACTERISTICS OF YAN'AN COMPACTED LOESS IN A FULL SUCTION RANGE INCORPORATING TEMPERATURE EFFECTS

In arid and semi-arid loess regions, the water retention and permeability characteristics of compacted soil roadbed and loess overburden layer of landfill are all affected by temperature variation. To investigate the influence of temperature variations on the hydraulic properties of compacted loess in a full suction range, we measured the soil-water characteristic curve(SWCC) and hydraulic conductivity curve(HCC) of compacted loess in Yan'an city with different temperatures using the filter paper method and the self-developed soil column instantaneous profile method. The results show that in the high suction range of compacted loess SWCC, the volumetric water content of soil decreases as temperature increases. While in the low suction range, the temperature effect on water retention capacity of soil is not obvious. The HCC of loess in the low suction range is significantly affected by temperature. The higher the temperature, the stronger the permeability. As the suction increases or the volumetric water content decreases to a specific value, the influence of temperature on soil permeability can be ignored. Based on the results, the modified van Genuchten(VG)model is used as the prediction function of SWCC with the temperature effect taken into account. The parameters related to temperature are obtained by fitting the measured data. For the HCC, the 90 kPa matric suction is taken as the subsection point. The statistical model and power function are respectively used for the subsection prediction in the low suction range and high suction range. The prediction results are in good agreement with the measured data.