The indirect estimation of saturated hydraulic conductivity of soils, using measurements of gas permeability. I. Laboratory testing with dry granular soils
Tony Wells A C , Stephen Fityus A , David W. Smith B and Hlwan Moe AA The School of Engineering, The University of Newcastle, Callaghan, Newcastle, NSW 2308, Australia.
B Department of Civil and Environmental Engineering, The University of Melbourne, Vic. 3010, Australia.
C Corresponding author. Email: Tony.Wells@newcastle.edu.au
Australian Journal of Soil Research 44(7) 719-725 https://doi.org/10.1071/SR06037
Submitted: 11 January 2006 Accepted: 25 July 2006 Published: 20 October 2006
Abstract
A comprehensive knowledge of soil hydraulic conductivity is essential when modelling the distribution of soil moisture within soil profiles and across catchments. The high spatial variability of soil hydraulic conductivity, however, necessitates the taking of many in situ measurements, which are costly, time-consuming, and labour-intensive. This paper presents an improved method for indirectly determining the saturated hydraulic conductivity of granular materials via an in situ gas flow technique. The apparatus employed consists of a cylindrical tube which is embedded in the soil to a prescribed depth. Nitrogen at a range of pressures was supplied to the tube and allowed to escape by permeating through the soil. A 3-dimensional, axisymmetric, steady-state, finite element flow model was then used to determine the value of the soil intrinsic gas permeability which produces the best fit to the pressure–air flow data. Saturated hydraulic conductivities estimated from the application of the gas flow technique to 5 granular soils covering a wide range of permeabilities were in close agreement with values determined using a conventional permeameter. The results of this preliminary study demonstrate the potential of this approach to the indirect determination of saturated hydraulic conductivity based on measurement of gas flow rates in granular and structured soils.
Additional keyword: finite element modelling.
Acknowledgments
This research has been carried out with financial support from the Australian Research Council (ARC). The numerical modelling was done using FEMLAB version 2.1 by COMSOL Inc, USA.
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