Experimental Study on Moisture Migration in Unsaturated Loess under Effect of Temperature
Publication: Journal of Cold Regions Engineering
Volume 24, Issue 3
Abstract
In this paper, moisture migration in loess considering temperature effect is studied by tests on unsaturated loess samples with different densities and initial moisture contents. Test results reveal that obvious changes in moisture content distribution in a loess sample can be observed after temperature difference is exerted on the two ends of the sample. Moisture content at the cold end increases and that at the hot end decreases. Under the effect of temperature difference, moisture content difference at the two ends of a soil sample is related to the initial moisture content, soil density, and magnitude of the temperature difference. Generally speaking, larger temperature differences and smaller soil densities result in more obvious moisture migration and larger moisture content differences at the two ends of the soil sample. When the initial moisture content is large, the moisture content difference caused by a temperature difference is small; when the initial moisture content is small, the moisture content difference caused by a temperature difference is also small; when the initial moisture content is moderate, the moisture content difference caused by a temperature difference is large. After the analysis of test results, taking the soil density and moisture content into account, a formula is obtained to determine the moisture content gradient resulting from the temperature gradient. Reliability of the formula is verified by comparing the measured and calculated data. Because of the reverse migration of liquid water and water vapor at the end of the experiment, it is difficult to determine the thermal potential and matrix potential. Based on the experimental data, this paper probes into the water potential equation that can be used for stability analysis. The equation considers the comprehensive impact of soil density, temperature gradient, moisture content, and moisture content gradient on water potential. It only applies to analyze stable distributions of temperature and does not apply to unstable temperature distributions.
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References
Cassel, D. K., Nielsen, D. R., and Bigger, J. W. (1969). “Soil-water movement in response to imposed temperature gradient.” Soil Sci. Soc. Am. Proc., 33, 483–500.
Heitman, J. L., Horton, R., Ren, T., Nassar, I. N., and Davis, D. (2008). “A test of coupled soil heat and water transfer prediction under transient boundary conditions.” Soil Sci. Soc. Am. J., 72, 1197–1207.
Heitman, J. L., Horton, R., Ren, T., and Ochsner, T. E. (2007). “An improved approach for measurement of coupled heat and water transfer in soil cells.” Soil Sci. Soc. Am. J., 71, 872–880.
Kong, X. -q. (1998). The finite element method in transmit heat, Science Press, Beijing (in Chinese).
Lam, L., Fredlund, D. G., and Barbour, S. L. (1987). “Transient seepage model for saturated-unsaturated soil system: A geotechnical engineering approach.” Can. Geotech. J., 24(4), 565–580.
Li, S., and Cheng, G. (1995). Issue of water and thermal transfer of frozen and thaw soil, Lanzhou University Press, Lanzhou, China (in Chinese).
Milly, C. P. D. (1982). “Moisture and heat transport in hysteretic, in homogeneous porous medias: A matrix head-based formulation and a numerical model.” Water Resour. Res., 18(3), 489–498.
Nassar, I. N., and Horton, R. (1999). “Salinity and compaction effects on soil water evaporation and water and solute distributions.” Soil Sci. Soc. Am. J., 63, 752–758.
Nassar, I. N., Horton, R., and Globus, A. M. (1992). “Simultaneous transfer of heat, water, and solute in porous media: II. Experiment and analysis.” Soil Sci. Soc. Am. J., 56, 1357–1365.
Nassar, I. N., Shafey, H. M., and Horton, R. (1997). “Heat, water, and solute transfer in unsaturated porous media: II. Compacted soil beneath plastic cover.” Transp. Porous Media, 27, 17–38.
Philip, J. R., and Vries, D. A. (1957). “Moisture movement in porous materials under temperature gradient.” Trans., Am. Geophys. Union, 38(2), 222–231.
Taylor, S. A., and Lary, J. W. (1964). “Linear equations for the simultaneous flux of matter and energy in a continuous soil system.” Soil Sci. Soc. Am. Proc., 28, 167–172.
Wang, T., Hu, C., and Li, N., (2002). “Numerical analysis of ground temperature in Qinghai-Tibet plateau.” Sci. China, Ser. E: Technol. Sci., 45(4), 433–443.
Wang, T. -h., and Zhao, S. -d. (2003). “Equation for water vapor transfer in unsaturated soil.” China Journal of Highway and Transport, 16(2), 18–21 (in Chinese).
Xie, D. -y. (2001). “Exploration of some new tendencies in research of loess soil mechanics.” Chinese J. Geotech. Eng., 23(1), 3–13 (in Chinese).
Zang, S. -m., and Zheng, J. -g. (1990). “The deformation characteristics of collapsible loess during moistening process.” Chinese J. Geotech. Eng., 12(4), 21–31 (in Chinese).
Information & Authors
Information
Published In
Journal of Cold Regions Engineering
Volume 24 • Issue 3 • September 2010
Pages: 77 - 86
Copyright
© 2010 ASCE.
History
Received: Sep 22, 2008
Accepted: Jan 7, 2010
Published online: Jan 9, 2010
Published in print: Sep 2010
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