Abstract
To reveal the water‐heat transfer mechanism of unsaturated loess, the effects of soil dry density (1.30 g/cm3, 1.50 g/cm3, and 1.65 g/cm3), moisture content (13.3%, 16.2%, and 19.4%), cold end temperature (−7°C, −10°C, and −13°C), and freezing mode on moisture migration in unsaturated loess in this paper are studied through indoor tests of moisture migration under the freezing action of large‐size unsaturated loess. The results show that the temperature change in soil samples in the freezing process can be divided into three stages: rapid cooling stage, slow cooling stage, and stable stage. The higher the dry density, the closer the freezing front is to the cold end, with the initial moisture content having little effect on the freezing front, while the temperature at the cold end has a significant effect on the location of the freezing front. The total amount of moisture migration decreases with the increase of dry density, increases with the increase of moisture content, and increases with the decrease of cold end temperature. The freezing mode directly affects the distribution of moisture content and total amount of moisture migration in the frozen area.
Highlights
China has a vast loess area, most of which is in the seasonally frozen region. e physical and mechanical properties of the topsoil in this region vary greatly as the superficial layer of loess is greatly affected by natural factors. e infiltration of rain in summer and autumn and the freezing of soil layer in winter increase the moisture content of the surface soil, and the shear strength decreases
In the rapid cooling stage, mainly between 0 and 48 hours, the closer it is to the cold end, the shorter the cooling time is; the slow cooling stage is mainly between 48 and 240 hours; the stable stage starts from 240 hours to the end of the test. e greater the dry density, the greater the thermal conductivity
The water in the soil sample releases more heat, and the released heat will prevent the temperature of the whole sample from falling. erefore, the effect of dry density on the temperature field of the sample still needs to be determined by test
Summary
China has a vast loess area, most of which is in the seasonally frozen region. e physical and mechanical properties of the topsoil in this region vary greatly as the superficial layer of loess is greatly affected by natural factors. e infiltration of rain in summer and autumn and the freezing of soil layer in winter increase the moisture content of the surface soil, and the shear strength decreases. A general survey of previous research results shows that existing studies have revealed the characteristics of soil moisture migration toward the freezing front, but lack of systematic study on the effects of factors such as soil density, moisture content, cold end temperature, and freezing mode, on moisture migration in unsaturated loess. This paper, through indoor freezing tests of large-size loess, studies the effects of soil dry density (1.30 g/cm3, 1.50 g/cm, and 1.65 g/cm3), moisture content (13.3%, 16.2%, and 19.4%), cold end temperature (−7°C, −10°C, and −13°C), and freezing mode on moisture migration in unsaturated loess, laying a foundation for analysis of the freeze-thaw disease mechanism of loess engineering
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