Validation of the percolation-based effective-medium approximation model to estimate soil thermal conductivity

Soil thermal conductivity (lambda) has broad applications in soil science, hydrology, and engineering. In this study, we applied the percolation-based effective-medium approximation (P-EMA) to estimate the saturation dependence of thermal conductivity (lambda(theta)$\lambda ( \theta )$) using data from 38 undisturbed soil samples collected across the state of Kansas. The P-EMA model has four parameters including a scaling exponent (ts), critical water content (theta c), and thermal conductivities at oven-dry (lambda dry) and full saturation (lambda sat) conditions. To estimate the lambda-theta$\lambda - \theta $ curve, the values of lambda dry and lambda sat were measured using a soil thermal properties analyzer and the values of ts and theta c were estimated as a function of clay content. Thermal conductivity was also estimated using the Johansen model. By comparison with observations, the P-EMA model resulted in a root mean square error (RMSE) ranging from 0.029 to 0.158 W m-1 K-1, whereas the Johansen model had an RMSE ranging from 0.021 to 0.173 W m-1 K-1. Our results demonstrate that the P-EMA model has comparable accuracy to the widely used Johansen model to estimate the saturation-dependent soil thermal conductivity of undisturbed soils with minimal input parameters. Future studies should focus on better understanding the physical meaning of ts and theta c in the P-EMA model to improve our ability to model thermal conductivity in undisturbed soil from percolation principles. Soil thermal conductivity was estimated using the percolation-based effective-medium approximation (P-EMA) model.We used a dataset of soil thermal properties measured in 38 undisturbed soil samples.The P-EMA model resulted in a root mean square error ranging from 0.029 to 0.158 W m-1 K-1, which was similar to the widely used Johansen model.

Automated summary

This study applied the percolation-based effective-medium approximation (P-EMA) model to estimate the saturation dependence of soil thermal conductivity. The results showed that the P-EMA model had comparable accuracy to the widely used Johansen model and required fewer input parameters. Future research should focus on better understanding the physical meaning of the model parameters to improve the ability to model soil thermal conductivity.