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Comparative study of numerical and laboratory methods for determining the hydraulic conductivity function of a sand

Abstract:

We compared experimentally measured hydraulic conductivity-water content relationships with those predicted by three models. Sand was the medium used for this comparative study. The laboratory methods used included: Instantaneous profile-internal drainge; infiltration through crust; hot air drying; pressure plate outflow; and unit gradient drainage. For the numerical approach, we used the Irmay, the Jackson, and the Mualem models. The moisture desorption curve and the saturated hydraulic conductivity were used as inputs. Additional parameters were estimated from the literature. We found close agreement between the K(θ) relationship measured according to the instantaneous profile method and estimates based on Irmay’s equation; Jackson’s prediction method, with a pore interaction exponent of 0.5; and Mualem’s model, with an effective saturation term exponent of 0.5. In addition, the predicted K(θ) relationship with the Mualem model, using 0.75 as exponent of the effective saturation term, and the predicted values with the Millington and Quirk equation (being Jackson’s model with p = 4/3), corresponded with the experimental relationship obtained by the gypsum-sand crust technique. The predicted K(θ) relationships obtained by the above models also matched the K(θ) values obtained by the hot air method in the wet range. © 1981 The Williams & Wilkins Co.