Frost-induced changes in the structure of sediments-Results after 500, 1 000, 1 500 experimental freeze-thaw cycles

Sediment samples composed of silt (<0.063 mm), fine- (0.125-0.250 mm) and coarse-sand (0.5-1.0 mm) fractions were subjected to freeze-thaw cycles under controlled laboratory conditions for a period of eight months. A total of 40 samples of different sediment arrangement, sediment packing, water content and mineralization were studied at 0 (prior to experiment) and after 500, 1 000, and 1 500 freeze-thaw cycles. Macroscopic and 3-D X-ray imaging observations of the sediment structure reorganisation were reported. The results indicate modifications in the vertical and horizontal sediment arrangement along with the development of frost-induced deformational structures and internal (inter-layer) inhomogeneities of the sediment fabric. The most commonly observed changes in the sediment structure originated from the experimental frost action are: modifications at the boundary between lithologically-different sediments, formation of cracks within sediment layers, changes in thickness of the individual layers, and development of sediment deformations. The vast majority of frost-induced modifications of the sediment structure are observed within the silt layer and at its boundaries with sand layers. The presence and frost susceptibility of silt sediment may be treated as a driving force that facilitates the process of sediment deformation during the freeze-thaw activity. Moreover, it was shown that changes in the sediment structure include both formation and obliteration of frost-originated features with the increase in the number of freeze-thaw cycles.