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Serious problems due to frost heaving and thaw settlement can be experienced by structures founded in seasonally and perennially frozen ground. Various design and construction techniques can be used to overcome or reduce the severity of these problems. One approach is to prepare and improve the properties of the foundation soil in advance of construction such that it is less susceptible to frost action and to settlement due to thawing. Much work has been done in the U. S.S.R. on this subject and this recently published manual is therefore of special interest in its studies of construction problems in permafrost areas. The manual describes electrical and chemical methods and techniques used in the Soviet Union for preconstruction preparation of seasonally and perennially frozen soils. The physical and mechanical properties of the foundation soil are improved by electrical thawing methods and/or injection of various chemicals followed by compaction of the soil, if required, before a structure is erected.

A soil frost susceptibility test is proposed. The method involves the unidirectional freezing of a saturated sample by imposing a step freezing temperature at one end of the specimen and measuring the heave rate. The two most important conditions that influence heave rate during the test are the overburden pressure and the freezing temperature. Results show that the heave rate can be expressed as an exponential function of the applied overburden/freezing temperature ratio. The desirable features of the proposed freezing technique and the method of interpreting the results are outlined., 3rd International Conference on Permafrost, July 10-13, 1978, Edmonton, Alberta, Canada

This translation is the third arranged by the Permafrost Subcommittee of the Associate Committee on Soil and Snow Mechanics of the National Research Council of Canada, of the Russian permafrost publication, "Principles of Geocryology". The first section of this translation of Chapter VII by I.Ya. Baranov discusses the global distribution, with emphasis on the U.S.S.R., of seasonally frozen ground. The largest portion of the text deals with the distribution of permafrost throughout the world. It includes information on the areal extent, thickness and temperature of permafrost, and variations in these characteristics from one physical region to another.

The frost heaving forces developed under a 1 ft (30.5 cm) diameter steel plate were measured in the field throughout one winter. The steel plate was fixed at the ground surface with a rock-anchored reaction frame. Heave gauges and thermocouples were installed at various depths to determine the position and temperature of the active heaving zone.The general trend was for the surface force to increase as the winter progressed. When the frostline approached maximum depth the force was in excess of 30 000 lb (13 608 kg). Estimates of the heaving pressure at the frostline ranged from 7 to 12 psi (0.49 to 0.84 kg/cm2) during this period.The variation of surface heaving force was closely associated with weather conditions. Warming trends resulting in a temperature increase of the frozen layer caused the forces to decline.

It is estimated that peatland covers more than one million square kilometres of Canada, extending from the southernmost part of the country to the Arctic in the continuous permafrost zone. This terrain has been subjected to increasing scientific and engineering study as northern development progresses. Many geotechnical engineering activities in Canada are affected by the freezing of peatland; the operation of off-road vehicles on peat terrain, the construction of oil and gas pipelines, and the erection of temporary structures all require information on the freezing process in peat terrain. The present paper is intended to give engineers and other workers a practical appreciation of the rate of freezing and thawing, depth of frost penetration and thaw, and the influence of climate and terrain on these processes. It is based on information available in the literature and on field observations at two sites, one the Mer Bleue peat bog near Ottawa in the zone of seasonal freezing, the other at Thompson, Manitoba, in the middle of the discontinuous permafrost zone.

One terrain feature of great significance to the extent, thickness and thermal regime of permafrost is vegetation. Its thermal properties determine the amount of heat leaving or entering the underlying ground. Vegetation has an indirect effect on climate, which influences permafrost. Treeless vegetation such as lichen and mosses may have a different albedo. Net radiation is also an important factor. Direct measurement of the convection component is extremely difficult and it may be evaluated as the difference between the sum of the other measurements and the total. Bowen's ratio is also sometimes used. Evaporation, including evapotranspiration, withdraws heat from the surrounding atmosphere and from incident solar radiation. Vegetation draws water by transpiration thus depleting the soil of heat held by that water. There are great variations between species. Vegetative cover of dead material has a large insulating effect on the underlying permafrost. Depth of thaw increases where vegetation cover has been removed. The micro climate resulting from vegetation is probably most effective by influencing the wind speed. The density of the vegetation and height of tree cover influences are well known. Ground that permits the greatest degree of water penetration usually thaws to the greatest depths. The low thermal conductivity of snow and its double role as inhibitor of frost penetration during winter and soil thawing in the spring has been noted. Where strong winds prevail more snow accumulates under vegetative cover in open areas. The most easily observed and measured characteristic of permafrost is the depth of thaw and variations in types of vegetation are often readily noticeable., Permafrost International Conference, November 1963