Influence of Freeze-Thaw Cycles and Soil State on Erodibility of Soils in Cold Regions

Oceanic erosion in arctic coastal areas experiences some of the highest erosion rates with an average rate ranging from 2 to 6 m/year and extreme events seeing as much as 20 m/event. The soils in these areas are characterized as having high soil-ice content and low densities due to the preexisting permafrost. Seasonal weathering cycles are not typically thought of as direct contributor to the high erosion rates in the arctic oceanic areas, but they can increase the amount of sediment susceptible to transport by erosion. With the increased susceptibility to erosion, it's much easier for mechanical wave action or groundwater runoff to transport the soil. Due to the high erosion rates of arctic coastal soils, the number of freeze-thaw cycles they experience is relatively small before the sediment is transported away exposing new soil. This study sought to investigate the impact that soil density, moisture content, and freeze-thaw cycles have on its erodibility. To accomplish this, a low plasticity soil was prepared at three different density and moisture content combinations, exposed to 0, 1, 2, 3, 4, and 5 freeze-thaw cycles, then their erosivity was measured at frozen, thawing, and thawed states to determine how soil-ice particle interactions change the soils erosivity. It was concluded that soil moisture content plays the largest role in the degradation effects that the soil mass experiences. With larger amounts of available water in the samples, the expansion forces generated during the freezing stage result in more pronounced breakdown of the soil fabric.