Prediction of soil solid thermal conductivity from soil separates and organic matter content: computational micromechanics approach

Publisher： John Wiley & Sons Inc

E-ISSN： 1365-2389|67|5|551-563

ISSN： 1351-0754

Source： EUROPEAN JOURNAL OF SOIL SCIENCE, Vol.67, Iss.5, 2016-09, pp. : 551-563

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Abstract

Evaluation of soil thermal conductivity at a given saturation usually requires the value of conductivity in the saturated state, which is commonly estimated by the geometric mean from the conductivities of water and soil solids (λ_s). Therefore, an accurate estimate of λ_s has a marked effect on soil conductivity within the full range of saturation. In this research, we modelled the soil solid as a multi‐phase medium comprising individual isotropic phases with conductivities drawn randomly from an assumed probability density function. The variation in the thermal conductivity of minerals is associated with the corresponding soil separates: clay, silt and sand. A computational micromechanics approach was used to evaluate the homogenized thermal conductivity of the soil solids with different fractions of soil separates and organic matter contents. A new formula to predict λ_s is proposed by fitting a four parameter, non‐linear function to the numerical results. Thirty experimental results of soil conductivities at saturation (our investigations and literature data) were used to validate the proposed model. We show that the new approach improves analytical predictions in terms of the root mean square error and bias. The proposed model to estimate λ_s is suitable for practical purposes because it requires information on the fraction of sand and organic matter contents only.

Highlights

Can we predict conductivity of solids from soil separates and organic matter only?Soil skeleton is modelled at the mineralogical scale as a multiphase material.Conductivity of soil solids has considerable effect on assessment of conductivity in the saturated state.Proposed model makes possible the efficient evaluation of thermal conductivity of soil solids.