Soil thermal properties determination and prediction model comparison

The thermal conductivity is one of the important thermal parameters. In order to get the method for accurately forecasting the thermal conductivity of soils, the heat-pulse direct measuring method and indirect calculation method were compared. According to the principle of heat-pulse, the thermal conductivity of soils with different textures and moisture in the same soil bulk density were measured. The results showed that, under the same moisture, the soil thermal conductivity increased with the sand content rise. Horton equation was used to fit the measured values. The results indicated that the Horton equation may be used to describe the relationship between thermal conductivity and water content, and the parameters in Horton equation were given. Campbell empirical formula of thermal conductivity was used to calculate the thermal conductivity. The results show that there was a large difference between the calculated and measured values. Johansen model and two improved models were used to calculate the thermal conductivity. The results showed that there was a deviation between Johansen model calculated values and measured values, and the results from two improved models were more consistent with measured values. The research indicated that soil thermal conductivity can be calculated by soil texture, water content, soil porosity and bulk density. The correlation coefficients of calculated values from C?té-Konrad model and Lu-Ren model with measured values were 0.643, 0.937 and 0.943, respectively. The two improved models are recommend for calculating soil thermal conductivity, and the application scope of Lu-Ren model is wider than that of C?té-Konrad model.