EXPERIMENTAL TESTS ON TEMPERATURE CHANGE OF SHALLOW UNSATURATED LOESS UNDER ATMOSPHERIC ACTION AND ITS INFLUENCING FACTORS

This paper aims to research the variation law of temperature field and its influencing factors of shallow unsaturated loess in the northwestern of China. A one-dimensional soil column model is built and placed under outdoor natural conditions. It is used to test the outdoor evaporation model under atmospheric temperature cycle. The experimental results show that the soil temperature decreases with the increase of depth in the depth range of 0~10cm, and the temperature is the lowest at 5~10cm in the surface layer of the soil sample. Under the same external conditions, the initial volume content of the soil is higher and the degree of compaction is higher. The larger the thermal conductivity and the greater the temperature change. As the depth increases and the evaporation time increases, the difference in thermal conductivity caused by compaction and water content is superimposed. So the temperature difference between soils with different compaction degrees and different water contents at the same depth increases. Both of the initial volume content of the soil and the compaction degree of soil have an effect on the temperature migration. Compared with the change of compaction degree, the change of soil volume content has a more significant effect on soil temperature migration. With the increase of evaporation time, the temperature gradually increases from the surface to the inside. The temperature in the depth direction decreases firstly and then increases. The soil temperature growth curve at different depths is roughly a "S" type increasing curve, which can be divided into three stages of evaporation.