Abstract
Water migration changes the water distribution of loess and significantly affects the engineering properties of loess. However, because of the characteristics of loess such as water sensitivity and special structure, it is still difficult to understand the water migration trend of loess. The objectives of this study are to investigate the water diffusion coefficient and soil-water characteristic curve (SWCC) of loess, focusing on the effect of temperature and density, and establish a mixed migration equation for gaseous and liquid water to develop a new calculation method of loess water migration. The results show that the density of loess with larger liquid water content has a more significant effect on the diffusion coefficient than that of less liquid water content. Furthermore, the density significantly affects the matric suction of unsaturated loess, while the temperature change at normal temperature has slight effect. Based on the data obtained in this study, the soil water permeability coefficient was obtained. Moreover, considering the characteristics of mixed migration of gas and liquid water in unsaturated loess, an equation was derived for the gas-liquid water transfer in unsaturated loess. The calculation results are consistent with the experimental results of water migration experiment. Based on the calculation results of water migration, the trend of water migration and proportion of gaseous water during migration were analyzed.
Highlights
Permeability coefficient is important to evaluate the permeability of unsaturated soil. e analysis and calculation of water movement require the measurement of permeability coefficient of unsaturated soil. e permeability coefficient of unsaturated soil has been extensively studied
Considering the characteristics of mixed migration of gas and liquid water in unsaturated loess, an equation was derived for gas-liquid water transfer in unsaturated loess. e data of water diffusivity and soil-water characteristic curve (SWCC) of loess were substituted into the equation for calculation
To measure the SWCC of unsaturated loess, a matric suction experiment was carried out. e physical properties of soil samples used in the experiment are the same as those of loess used in the water diffusion experiment. e SWCC was measured using a high-speed centrifuge (Hitachi cr21g PF)
Summary
Permeability coefficient is important to evaluate the permeability of unsaturated soil. e analysis and calculation of water movement require the measurement of permeability coefficient of unsaturated soil. e permeability coefficient of unsaturated soil has been extensively studied. Lemoubou et al [2] developed an estimation method for unsaturated soil permeability parameters considering the effect of volumetric liquid water content. Tian et al [5] studied the effect of volumetric liquid water content on the permeability coefficient of unsaturated loess under steady state. Zhang et al [13] reported that the permeability coefficient of unsaturated loess is affected by pore characteristics, and the pore characteristics of loess with different densities and water contents under different pressures were studied. E objectives of this study are to investigate the water diffusion coefficient and soil-water characteristic curve (SWCC) of loess, focusing on the effect of temperature and density, and derive a mixed migration equation for gaseous and liquid water, developing a new calculation method for loess water migration. Considering the characteristics of mixed migration of gas and liquid water in unsaturated loess, an equation was derived for gas-liquid water transfer in unsaturated loess. e data of water diffusivity and SWCC of loess were substituted into the equation for calculation
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