Effect of freeze-thaw cycle on the parameters of the Green and Ampt infiltration equation

In humid and temperate regions, application of hydrologic models based on t he Green and Ampt infiltration equation, during the spring season, often cr eates problem due to freezing and thawing of soils. These climatic conditio ns result in significant changes in hydrological and hydraulic properties o f the soil. Three soil properties which are used to estimate parameters of the Green and Ampt infiltration equation were measured on repacked soil cor es after subjecting them to a number of freeze-thaw cycles. The saturated h ydraulic conductivity, air entry potential and total porosity tests were co nducted to determine the influence of repeated freeze-thaw cycles on these properties and to incorporate the interactive effect of soil type, bulk den sity and saturation on these variables. The three soil types chosen for the experiment were silt loam, clay loam and loamy sand. Saturated hydraulic c onductivity was measured using a steady upward flow constant head permeamet er. The air-entry potential was estimated from the relationship between soi l matric head and volumetric water content. Volumetric water content at sat uration was used to approximate total porosity. Results from factorial anal ysis of variance indicate that the means of saturated hydraulic conductivit y, total porosity and air-entry potential proved to be significantly differ ent among soil types and bulk density. Changes in saturated hydraulic condu ctivity values for the three different soil types by the impact of continuo us freeze-thaw cycles is most severe at lower degree of saturation and redu ces in severity as the degree of saturation increases. (C) 1999 Silsoe Rese arch Institute.