Abstract | Snow is an important road building material in countries with cold winters. Primitive snow roads are compacted by the traffic itself, but better quality roads are artificially compacted and maintained. The important factor quantatively determining the state of snow is temperature. Freezing causes the growth if ice crystals concentrating foreign substances at the surfaces giving lower freezing temperatures, which account for the friability of snow in spring. Compaction of snow causes ice crystals to fuse giving high strength to the total mass. Snow continuously undergoes structural changes as the temperature changes. These are greater near the snow interface with the air because of greater temperature fluctuations. Sublimation, the change in state from a solid to a gas, is an important phenomenon causing structural changes within the snow mass. Colder air temperatures cause the snow near the air/snow surface to densify by crystal growth through the vapour phase; at lower depth vapour losses reduce the density. The low bearing capacity of freshly fallen snow causes traffic problems, as does coarse-grained "corn" snow. Compaction is the most important snow hardening process, but the degree of success depends on the thickness of the snow mass, the time interval between snow falls and the time of day when the compaction is carried out. Afternoons are considered more favourable for compaction because the temperatures are higher, giving the highest liquid content. Cold night temperatures harden the snow by freezing the liquid. It is concluded that it is now possible to build good traffic- bearing snow roads that can connect isolated communities during the long winter period in cold climates. |
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