Soil Mound Formation by Multicyclic Freeze-Thaw
摘要
Experiments are being carried in freezing cabinets in order to determine the effect of many cycles of freezing and thawing in a layered soil 4 cm thick. The soil was composed of three hori-zontal layers, two layers of silty-clay and a layer of crushed quartz in between; each layer was 1.3 cm thick. Moisture was supplied from the bottom and thawing from the top. Through the experiment the soil was saturated; average rate of freezing was 1 mm per hour, rate of thawing 2 mm per hour. During the first 28 cycles only a broad mound was developed; after that small mounds 1-2 cm at the base started to form. The maximum height of mounds was 2 cm. The number of mounds reaching a certain height indicates that the rate of mound growth is higher through cycles 28-37; after that the rate of growth decreased. The form of the mounds is not upright cone; they are inclined and near the top the material is inclined to horizontal. It is proposed as a very qualitative approach that these mounds are produced by the release of pressure during freezing. Pressure is released in the freezing layer in loci with the highest per-centage of unfrozen water. To such places of unfrozen water the migration of particles and water takes place. The extrusion of particles at the upper part of the mound is an indication of such migration. It is believed that this is the first report on experimental formation of soil mounds. I.