The Importance of freezing rate in frost action in soils

This study was concerned with determining the effect of rate of freezing on frost action under laboratory conditions. This was done for the saturated and near-saturated moisture conditions of the soil. The rate of freezing was measured both in terms of heat flow and rate of frost penetration. Three soils of widely differing properties were used to bring out major differences in behavior to freezing. The results show a positive relation between net heat flow or frost penetration rate and heaving rate. Increasing the rate of heat flow away from the freezing plane in all cases increased the rate of moisture flow to the freezing plane and consequently also the heaving rate. This was shown to be true for the three soils studied at high moisture contents. It is not correct to compare the frost susceptibility of different soils in laboratory freezing experiments on the basis of equal rates of frost penetration when, in fact, this does not occur in the field. The rate of heat extraction used in laboratory tests of frost heaving should be related to the actual heat flow in the environment of the soil. The results presented should be useful in setting up practical laboratory freezing procedures for the realistic evaluation of the frost susceptibility of soils in the field.