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

Abstract

AbstractSoil thermal conductivity (λ) 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 () 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 (θc), and thermal conductivities at oven‐dry (λdry) and full saturation (λsat) conditions. To estimate the curve, the values of λdry and λsat were measured using a soil thermal properties analyzer and the values of ts and θc 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 θc in the P‐EMA model to improve our ability to model thermal conductivity in undisturbed soil from percolation principles.