Thermophysical properties of the soil massif

Grounds and foundations, underground structures

Calculations show that a significant percent of the heat losses of monolithic foundations consists of heat loss to the ground from concrete during construction. Therefore, ignoring heat losses to the ground (i.e., taking into account only the formwork and thermal insulation) leads to significant deviations between calculated and actual technological parameters. The existing methods for calculating the coefficient of heat transfer of enclosures are not suitable when calculating this same parameter for soil massifs. While finite thicknesses are used in this calculation for enclosures, thickness is infinite for soil massifs. To create a method for calculating heat losses to the ground, we solved a differential equation of heat conduction using integral transform methods. In the classical theory of heat transfer, for any material of finite thickness, the heat transfer coefficient is constant over time. However, for an array of soil, this parameter varies depending on period of time during which concrete loses heat to the soil. At the same time, the heat transfer coefficient increases with increasing soil density, which is explained by the growing contact area between particles in a unit volume of soil. Thus, the surface area through which the heat flux moves also increases. The article presents the results of the finite element calculation in the simulation software ELCUT, confirming the reliability of the obtained analytical dependencies.