Analysis and modeling of soil shrinkage and swelling dynamics as a function of predrying intensity and frequency and its influence on soil hydraulic properties
Final Report Abstract
We introduced an inexpensive, nondestructive and quantitative measurement of soil shrinkage in 2D. With this method the development of soil surface cracks during dehydration can be monitored. Nondestructive measurements of surface cracks could be used to identify crack volume. This method can improve our understanding of soil shrinkage and swelling in 2D. The geometry factor showed anisotropy of the vertical and horizontal soil deformation and depended on soil water content. Soil structure and pore shrinkage were influenced by inherent soil properties and by wetting and drying cycles. Organic-rich soils showed similar shrinkage behavior, with more shrinkage and less swelling during wetting and drying cycles than inorganic soils. Inorganic soils, with a higher clay content, were more sensitive to deformation. The pore size distribution and pore shrinkage capacity were modified significantly, if the maximal predrying stresses were exceeded. Hysteresis was found in soil volume changes as a function of water content during shrinkage and swelling. After a complete wetting and drying cycle, the volume of the soil did not return to its initial condition, so the swelling limit point could not be defined as the end point of structural shrinkage. We found that the swelling curve was composed of two characteristic parts, as defined as virgin swelling and residual swelling. The virgin swelling accounted for most of the volume increase during swelling, where the volume of the soil linearly related to water content. Shrinkage curves of transiently- and constantly-loaded soils are different through altering the rigid and non-rigid pores. The transient stress can only compact rigid pores, especially macropores, whereas the non-rigid pores are independent. However, the constant stress can alter fine non-rigid pores through restricting their swelling during wetting, besides reducing rigid pores. Therefore, the change of rigid pores does not modify pore shrinkage capacity, but the restricted non-rigid pores suppress their shrinkage. As a result, the transiently-loaded soil shrinkage curves are parallel to each other. The constantly-loaded soil shrinkage curves are finally intersected at zero shrinkage, or the dry-end point if the rigid pores are not altered. The stress-dependent rigid and non-rigid pores further cause different soil water release properties. The two different soil shrinkage curves can be modeled well by our proposed model.
Publications
- (2006): Physical soil properties of paddy fields as a function of cultivation history and texture. In: Hörn, R. Fleige, H., Peth, S., and Peng, X. 2006. Soil Management for sustainability. CATENA VERLAG, Reiskirchen, Germany, Advances in GeoEcology 38, ISBN 3-923381-52-2, 446-455
Janßen I., X. Peng & R. Horn
- 2006. Changes of nonrigid pore structure upon predrying intensity, frequency and history. 18th World Congress of Soil Science, July Philadelphia. USA
Peng, X., Horn, R.
- 2006. Extrapolating shrinkage of homogenized soils from wet bulk density and texture. 17th International Soil Tillage Research Organization. August, Kiel. Germany
Peng, X., Horn, R.
- 2006. Quantification of soil shrinkage in 2D by digital image processing of soil surface. Soil & Tillage Research. 91:173-180
Peng, X., Horn, R., Peth, S., and Smucker, A.
- 2006. Soil Management for sustainability. CATENA VERLAG, Reiskirchen, Germany ISBN 3-923381-52-2. Advances in Geoecology. 38
Hörn, R., Fleige, H., Peth, S., and Peng, X.
- 2006. Soil Shrinkage behavior as affected by bulk density and texture. Proceedings of ISTRO 17. 1486-1491. (ISBN 3-9811134-0-3)
Peng, X., and Horn, R.
- 2006. Wetting and drying cycle modifications of pore hysteresis of inorganic and organic soils. Deutsche Bodenkundliche Gesellschaft Annual Meeting, November, Leipzig, Germany
Peng, X., Horn, R.
- Auswirkungen der Bodengefügedynamik unter Nassreisanbau auf Porengrößenverteilung und Schrumpfungsverhalten. DBG Kommission I-Tagung Leipzig, 17.-18.11.2006
Janßen I., X. Peng & R. Horn
- Effect of puddling on physical soil properties of paddy fields. XVI Brazilian Meeting of Soil and Water Conservation and Management 23-27 of July 2006, Aracaju, Brazlian
Janßen I., X. Peng, J. Miguel Reichert, D. J. Reinert and R. Horn
- Physical soil properties of paddy fields as a function of cultivation history and texture. International Soil Tillage Research Organisation, 17th Triennial Conference, Aug 28-Sep 3rd, 2006 Kiel, Germany
Janßen I., X. Peng & R. Horn
- (2007): Auswirkungen der Bodengefügedynamik unter Nassreisanbau auf Porengrößenverteilung und Schrumpfungsverhalten. Mitt. Dt. Bodenk. Ges. 109, 16-17. ISSN-0343-1071
Janßen L, X. Peng & R. Horn
- 2007. Anisotropie shrinkage and swelling of some organic and inorganic soils. European Journal of Soil Science. 58:98-107
Peng, X., and Horn, R.
- 2007. Pore shrinkage dependency of inorganic and organic soils on wetting and drying cycles. Soil Science Society of America Journal. 71:1095-1104
Peng, X., Horn, R., Smucker, A.
