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Civil-Comp Proceedings
ISSN 1759-3433 CCP: 85
PROCEEDINGS OF THE FIFTEENTH UK CONFERENCE OF THE ASSOCIATION OF COMPUTATIONAL MECHANICS IN ENGINEERING Edited by: B.H.V. Topping
Paper 79
A Numerical Procedure for Fitting the Parameters used by the Kosugi Model to Predict Hydraulic Properties of Bi-Modal Soils L. Jendele1 and M. Kutilek2
1Cervenka Consulting, Prague, Czech Republic
Full Bibliographic Reference for this paper
L. Jendele, M. Kutilek, "A Numerical Procedure for Fitting the Parameters used by the Kosugi Model to Predict Hydraulic Properties of Bi-Modal Soils", in B.H.V. Topping, (Editor), "Proceedings of the Fifteenth UK Conference of the Association of Computational Mechanics in Engineering", Civil-Comp Press, Stirlingshire, UK, Paper 79, 2007. doi:10.4203/ccp.85.79
Keywords: soil, Kosugi, bi-modal, saturation, retention, hydraulic conductivity, constitutive model, fitting.
Summary
The paper presents a numerical procedure for fitting the material parameters of the Kosugi model that has been extended for bi-modal soils [1]. It is used to predict soil water saturation and hydraulic conductivity curves. The model was successfully used for several soil types and delivers more accurate results than other well established models. The fitting procedure itself employs the Quasi-Newton, Powell or Levenberg-Maquardt method. Based on our experience, the Powell method is recommended.
The constitutive model is characterized by the following two equations:
The first one predicts degree of effective soil saturation Si as a function of the hydraulic head of the capillary pressure hi. The second equation is used to calculate the soil relative hydraulic conductivity KRi. The model is employed for bi-modal soils, i.e. the two equations must be written separately for the matrix, (i=1) and structural pores, (i=2) and the procedure of fitting searches for optimal values of parameters hm1, hm2,
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() The procedure described proves robust and efficient. It converges within a reasonably short time, thereby it allows use of the Kosugi model for bi-modal soils. Based on the present procedure a computer program was developed to automate the whole process of the parameter fitting. References
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