Analysis of Thermal Parameters Variability During Thawing of Cohesive and Non-cohesive Soils

Abstract

Storage of heat and cold in the subsoil creates a need to identify the long-term variability of soil behavior under freezing and thawing conditions. Phase change cycles during the system operation can lead to deterioration of the soil in the immediate vicinity of the heat exchanger and changes in its thermal properties. The article presents the influence of phase transformation on the change of thermal properties of soil (thermal conductivity, thermal resistivity, volumetric heat capacity, thermal diffusivity). Samples of cohesive and non-cohesive soils, i.e. medium sand, silt and clay, were analyzed. Samples prepared according to the previously developed methodology were frozen at temperature of about -20°C, then were subjected to thawing at defined temperature. The temperature change of the sample was monitored during the measurement of thermal parameters (transient line source method). At the same time the temperature change in the part of the sample not affected by the thermal needle heating phase were observed.