Improvement of Salt-affected Soils, Part 4: Heat Transfer Coefficient and Thermal Conductivity of Salt-affected Soils

A new method was investigated for the improvement of salt-affected soils in regions where a sufficient amount of rainfall occurs in summer and the heat transfer coefficient and thermal conductivity of their soils were discussed. The subsoil is made coarse by soil sintering, and the capillarity from groundwater is cut-off. Thus, the rise to the soil surface of salts which are dissolved in the groundwater is prevented, and even if the groundwater level is high, the evaporation of water from the soil surface is reduced. In this paper, the heat transfer coefficient and thermal conductivity of the salt-affected soils were determined at the sintering temperatures (850–950 °C) in order to obtain basic data for soil sintering. Based on these values, design and construction of a device for soil sintering will be described in a subsequent report.The results show that the heat transfer coefficient to the steel surface was about 40 W m−2K−1 in the range of 280–320 °C. The heat transfer coefficient of the studied soil surfaces was about 60 W m−2K−1 in the range of 700–1000 °C regardless of types of soil.The thermal conductivity of pseudogley soil from Japan was about 0·1 W m−1K−1 (specimen temperature was about 900 °C, and soil water content was 0% dry basis) when the solid ratio was less than 0·38, and it was about 0·3 W m−1K−1 when the solid ratio was more than 0·38. The thermal conductivity of solonchak and solonetz from China was 0·1–0·3 W m−1K−1 (specimen temperature was about 900 °C, and soil water content was 0% dry basis) regardless of the types of soil and horizon. The thermal conductivity of the upper layer soils of the solonchak and solonetz did not increase with greater solid ratio because salts contained in them make for a low thermal conductivity.