Involutions resulting from annual freeze-thaw cycles: a laboratory simulation based on observations in northeastern Japan

A pilot laboratory experiment using a reversed two-layer soil model simulated small-scale involutions formed in a seasonal frost environment during the last glacial period. At the modelled site, the interface between the upper aeolian sandy loam and the lower volcanic pumice constitutes small-scale involutions that display upward-extending tapered projections and downward-extending round hollows. Two scale-reduced laboratory models were subjected to three accelerated annual freeze-thaw cycles with monitoring of frost heave, soil temperature, moisture and pressure. Ice segregation near the layer interface induces upheaving of coarse pumice grains on freezing and earlier settlement of mobilised loam on thawing, resulting in deformation of the interface. A reconstructed 3-D interface displays mounds and depressions with a diameter of 15-20 cm and a height increasing with freeze-thaw alternations. The experimental results imply that the repetition of differential heave and soft-loam settlement promotes decimetre-scale involutions in near-saturated soils subject to deep seasonal frost penetration. Copyright (C) 2007 John Wiley & Sons, Ltd.