Estimation of van Genuchten SWCC model for unsaturated sands by means of the genetic programming

Document Type : Article


1 Department of Civil Engineering Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran

2 Department of water and Natural Environment, Laboratory of Soil Mechanics, Isfahan Higher Education and Research Institute (IHEARI)

3 Department of Civil Engineering, Isfahan University of Technology (IUT), Isfahan, Iran


The van Genuchten Model (1980) is widely-used for the description of the Soil-Water Characteristic Curve (SWCC) of a variety of soils. This study uses the Genetic Programming (GP) for the presentation of equations estimating the van Genuchten (vG) Model fitting parameters for unsaturated clean sand soils. Moreover, this study uses the data derived from the valid dataset of Benson et al. (2014), including 95 measured SWCCs in both drying and wetting phases. The data on the particle size distributions includes the fine-grain percentage (Fines %), d60, d10, besides the residual and saturated volumetric water content and ), as the GP model inputs of set of terminal. As for the model outputs of set of terminal, the fitting parameters for the vG model include a and n. The functions used in the GP training were 'plus', 'minus', 'times', taken from the MATLAB default functions, 'mydivide' proposed by Silva (2007), and some other new power functions included by this study. Accordingly, new equations were presented for the estimation of vG Model fitting parameters for both forms of wetting and drying. Finally, to evaluate the accuracy of the proposed estimation equations, the GP results were evaluated and verified in different procedures.


Main Subjects


1. Krishnapillai, S.K. and Ravichandran, N. New soilwater
characteristic curve and its performance in the
A. Taban et al./Scientia Iranica, Transactions A: Civil Engineering 25 (2018) 2026{2038 2037
nite-element simulation of unsaturated soils", Int. J.
Geomech., 12(3), pp. 209-219 (2012).
2. ASTM standard D 6836-02, test methods for determination
of the soil-water characteristic curve for
desorption using a hanging column, pressure extractor,
chilled mirror hygrometer, and/or centrifuge annual
book of ASTM standards", 04.08, ASTM International,
West Conshohocken, PA (2003).
3. Nam, S., Gutierrez, M., Diplas, P., Petrie, J., Wayllace,
A., Lu, N., and Munoz, J.J. Comparison of
testing techniques and models for establishing the
SWCC of riverbank soils", Eng. Geol., 110(1-10), pp.
33-47 (2009).
4. Wang, M., Pande, G.N., Kong, L.W., and Feng, Y.T.
Comparison of pore-size distribution of soils obtained
by di erent methods", Int. J. of Geomech., 17(1), pp.
1-6 (2017).
5. Brooks, R. and Corey, A. Properties of porous media
a ecting
ow", J. Irrigation and Drainage Division,
ASCE, 92(2), pp. 61-88 (1966).
6. van Genuchten, M. A closed-form equation for predicting
the hydraulic conductivity of unsaturated
soils", Soil Science Society of America J., 44(5), pp.
892-898 (1980).
7. Fredlund, D.G. and Xing, A. Equations for the soilwater
characteristic curve", Can. Geotech. J., 31(4),
pp. 521-532 (1994).
8. Kosugi, K. General model for unsaturated hydraulic
conductivity for soils with lognormal pore-size distribution",
Soil Sci. Soc. Am. J., 63, pp. 270-277 (1999).
9. Omuto, C.T. Biexponential model for water retention
characteristics", Geoderma., 149(16), pp. 235-242
10. Frydman, S. and Baker, R. Theoretical soil-water
characteristic curves based on adsorption, cavitation,
and a double porosity model", Int. J. Geomech., 9(6),
pp. 250-257 (2009).
11. Yang, H., Rahardjo, H., Leong, E.C., and Fredlund,
D.G. Factors a ecting drying and wetting soilwater
characteristic curves of sandy soils", Canadian
Geotechnical Journal, 41, pp. 908-920 (2004).
12. Arya, L.M., and Paris, J.F. A physicoempirical model
to predict the soil moisture characteristic from particlesize
distribution and bulk density data", Soil Sci. Soc.
Am. J., 45(6), pp. 1023-1030 (1981).
13. Simms, P.H. and Yanful, E.K. Predicting soilwater
characteristic curves of compacted plastic soils
from measured pore-size distributions", Geotechnique,
52(4), pp. 269-278 (2002).
14. Romero, E. and Simms, P.H. Microstructure investigation
in unsaturated soils: a review with special attention
to contribution of mercury intrusion porosimetry
and environmental scanning electron microscopy",
Geotechnical and Geological Engineering, 26(6), pp.
705-727 (2008).
15. Ghanbarian, B., Taslimitehrani A., Dong, G., and
Pachepsky, Y.A. Sample dimensions e ect on prediction
of soil water retention curve and saturated
hydraulic conductivity", Journal of Hydrology, 528,
pp. 127-137 (2015).
16. Rawls, W.J., Gish, T.J., and Brakensiek, D.L. Estimating
soil water retention from soil physical properties
and characteristics", Adv. Soil Sci., 16, pp. 213-
234 (1991).
17. Zapata, C., Houston, W., Houston, S., and Walsh, K.
Soil-water characteristic curve variability", Advances
in Unsaturated Geotechnics, pp. 84-124 (2000).
18. Benson, C.H., Chiang, I., Chalermyanont, T., and
Sawangsuriya, A. Estimating van Genuchten parameters
a and n for clean sands from particle size
distribution data", ASCE GSP, pp. 234-235 (2014).
19. Johari, A., Habibagahi, G., and Ghahramani, A.
Prediction of soil-water characteristic curve using
genetic programming", Journal of Geotechnical and
Geoenvironmental Engineering, 132(5), pp. 661-665
20. Garg, A., Garg, A., Tai, K., Barontini, S., and
Stokes, A. A computational intelligence-based genetic
programming approach for the simulation of soil water
retention curves", Transp. Porous Media, 103(3), pp.
497-513 (2014b).
21. ASTM Standard D422-63 Standard test method for
particle-size analysis of soils, annual book of ASTM
standards", ASTM International, 04.08, West Conshohocken,
PA, pp. 129-145 (2003).
22. Koza, J.R., A Paradigm for Genetically Breeding
Populations of Computer Programs to Solve Problems,
Computer Science Dept., Stanford Univ., Margaret
Jacks Hall, Stanford, Calif (1990).
23. Silva, S. GPLAB: A genetic programming toolbox for
MATLAB", Available at
(veri ed 25 July 2007), Coimbra, Portugal (2007).
24. Parasuraman, K., Elshorbagy, A., and Si, B.C. Estimating
saturated hydraulic conductivity using genetic
programming", Soil Sci. Soc. Am. J., 71, pp. 1676-
1684 (2007b).
25. Baker, K. Investigation of direct and indirect hydraulic
property laboratory characterization methods
for heterogeneous alluvial deposits: application to the
sandia-tech vadose zone in ltration test site", MS Thesis,
New Mexico Institute of Mining and Technology,
Socorro, NM (2001).
26. RMA Rocky Mountain Arsenal", Final RCRAequivalent
cover demonstration project comparative
analysis and led demonstration scope of work", Dec.
1997, Rocky Mountain Arsenal Remediation Venture
Oce, Commerce City, CO (1997).
2038 A. Taban et al./Scientia Iranica, Transactions A: Civil Engineering 25 (2018) 2026{2038
27. Rassam, D. and Williams, D. A numerical study of
steady state evaporative conditions applied to mine
tailings", Canadian Geotechnical J., 36, pp. 640-650
28. Lu, N. and Likos, W., Unsaturated Soil Mechanics,
John Wiley, Hoboken, NJ, p. 556 (2004).
29. Likos, W., Wayllace, A., Godt, J., and Lu, N. Modi
ed direct shear apparatus for unsaturated sands at
low suction and stress", Geotechnical Testing J., 33(4),
pp. 286-298 (2010).
30. Tanahashi, H., Sato, T., and Konishi, J. Degree of imbibition
and residence oil saturation in porous media",
Proc. Creation of a New Geoenvironment, Fourth Kansai
International Geotechnical Forum, Kansai Branch
of the Japanese Geotechnical Society, Kyoto, Japan,
pp. 167-172 (2000).
31. Baker, R. and Hillel, D. Laboratory test of a theory
of ngering during in ltration into layered soils", Soil
Science Society of America J., 54, pp. 20-30 (1990).
32. Stormont, J. and Anderson, C. Capillary barrier e ect
from underlying coarser soil layer", J. Geotechnical
Geoenvironmental Engineering, ASCE, 125(8), pp.
641-648 (1999).