Leong and Rahardjo (1997) Estimation

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Leong and Rahardjo (1997) presented an equation which is comparable to the Fredlund and Xing (1994) SWCC curve raised to a power. The Leong and Rahardjo (1997) equation has been implemented into the SVFLUX software. A minimum value is also implemented as a restriction applied at high suction values.


It should be noted that the use of the Leong and Rahardjo (1997) unsaturated hydraulic conductivity function requires that the SWCC be represented by the Fredlund and Xing (1994) SWCC equation. The implementation is consistent with that suggested by the authors in their original research paper.


Leong p:

The Leong p parameter is the exponent to which the Fredlund and Xing (1994) SWCC equation is raised.


k minimum:

The k minimum value entered in this field represents the minimum allowable hydraulic conductivity. The minimum hydraulic conductivity should not be less than 1e-14 m/s. This value is assumed to be the point at which vapour flow begins to dominate moisture movement. Selecting a k minimum value less than 1e-10 m/s may significant increases in the number of nodes used to solve the problem. It is suggested that a minimum value of 1e-10 m/s be used for most practical problems. The user can then reduce the k minimum value until convergence difficulties are encountered.


Apply k minimum:

The equation originally presented by Leong and Rahardjo (1997) did not place a limitation on the minimum allowable hydraulic conductivity. Applying a reasonable minimum to the unsaturated portion of the curve can improve numerical computations.


Leong Predicted:

The Leong Predicted field indicates whether the fit algorithm has been successfully executed on the current data.


Leong Error:

The Leong Error is the difference between the fitted results and the laboratory values in terms of R2.



The Estimate button is provided at the bottom of the dialog in order to allow the user to estimate the hydraulic conductivity.



The Graph button allows the user to display a graph of suction versus hydraulic conductivity. The interpolated curve will also be displayed. It is important to note that laboratory data will be interpolated on an arithmetic scale.