Study on thermal conductivity model of saline soil based on particle morphology

Thermal conductivity of soils is significant on the thermal simulations in cold region engineering. Based on the generalized thermal conductivity for geotechnical materials, a thermal conductivity model for saline soil was proposed in this paper. At the micro level, the microstructure composition of sodium sulfate soils in the proposed model was redefined. Macroscopically, the variation of salt crystals and ice crystals with temperature and the relationship between the arrangements of components (i.e., liquid water, ice, soil particles) of saline soil were studied. Shape parameters α , β , τ were adopted to define the volume proportion of needle shape soil particles, spherical shape soil particles and disk shape soil particles, respectively. Besides, the proposed thermal conductivity model considered the heat loss due to the heat radiation in the measurement process. Furthermore, the accuracy of the proposed model was verified by the experimental data. The results showed that the soil particles can be defined as SWCA (i.e., soil particles, water, crystals mixture of salt and ice, air) four-layer concentric structure in the calculation of the thermal conductivity model of saline soil. Shape parameters have significant influence on simulation results. By comparing test data with calculated values, it can be found that at positive temperature, silty clay soil particles are mainly spherical ( β = 0.5) and disc-shaped ( τ = 0.5), while the sandy soil and soil-rock particles are more similar to the needle shape ( α = 1.0). With the decrease of temperature, the particle parameters of silty clay soil change, β decreases to 0, τ increases to 0.75, and α increases to 0.25. However, at negative temperature, the soil particles of sandy soil and loess are still mainly needle-shaped ( α = 1.0).