More than 50% of annual soil loss in a number of temperate regions of the world occurs when frozen soils are thawing. Such losses occur as a consequence of relatively high surface soil water contents due to the presence of a subsurface impermeable layer. This laboratory study addressed the soil mechanical principles governing erosion of soils with an impermeable subsurface layer (frozen or compacted, etc.). We examined (i) the effect of a freeze–thaw cycle on soil cohesion and (ii) the effect of a subsurface impermeable layer on soil detachment during raindrop impact for two soils: a Galva loess (silty clay loam, mixed, mesic Typic Hapludoll) and a Nicollet glacial till (loam mixed, superactive mesic Aquic Hapludoll). A Mohr diagram was constructed, based on a series of triaxial tests at three matric potentials. Soil cohesion for each treatment was determined from the Mohr diagrams. Soil water content treatments of 0.15 and 0.25 g g −1 were imposed before freezing and thawing. The freeze treatment was 90 min at −12°C, followed by a 30‐min thaw period. Immediately thereafter, shear strength and detachment were measured. Soil cohesion values were <50 kg m −2 and were not affected by freezing or by water content‐at‐freezing. The single‐water‐drop detachment values for soils with an impermeable layer vs. without an impermeable layer increased from 0.016 ± 0.0065 g to 0.054 ± 0.0265 g for loess and 0.036 ± 0.0071 g to 0.145 ± 0.0635 g for till. With an impermeable subsurface layer, soil matric potential is driven towards 0 Pa, resulting in extremely weakened soils prone to high soil‐detachment values and quite likely high soil‐erosion losses.
No takes yet. Share an insight, caveat, or question.
Froese et al. (1999) studied this question.