Thermal aspects of frost action

The paper relates to an experimental study of frost action in granular soils. The basic soil matrix of sand and ground chalk is highly frost susceptible. Coarse particles - 3.35mm-20mm - were blended with the matrix to produce mixtures containing 30 percent of coarse particles. Such treatment transformed the highly frost susceptible matrix to non-frost susceptible mixture. This was determined by measuring the frost heave developed by freezing specimens in a Controlled Heave Unit (CHU). This equipment was modified so that the thermal aspects of frost action could be modelled. Such parameters as heat flow and water intake could be measured. The rate of heave was dependent on the rate of heat extraction and, with constant boundary conditions, the thermal conductivity of soil became a governing factor. This parameter being controlled by the amount and type of coarse aggregate. The data has been examined to assess the role of these coarser particles in the freezing process and of particular interest was thermal conductivity of these mixtures. Heat flow, frost heave and water intake were examined for the matrix when tested under a wide range of boundary conditions and these included the warm-side and cold-side temperatures.