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Ice lenses in natural soil are normally formed in a thermal gradient regime, and this permits the development of an undulating frost line if a range of pore sizes exists. Evidence is presented that suggests that the undulating nature of the ice-water interface permits the ice lens to form over the smaller pores of the system. Although fractions with only a limited particle size range have been studied, the results support the use of particle size as a valid basis for assessing frost susceptibility.

The purpose of roads in areas of seasonal frost is to attenuate frost penetration and thus permit the design pavement thickness to be reduced. Early indications from actual use are that polystyrene insulation will meet these requirements. Two 100-ft (32.8-m) sections of street were constructed in Sudbury, Ontario, Canada, in September 1964 using 2-by-4-ft by 2-in. (0.610-by l.220-m by 5.08-cm) sheets of extruded polystyrene insulation in the pavement structure at a depth of 16 in. (0.406 m). In the summer of 1965 two additional insulated road sections were constructed in Ottawa, Ontario, Canada. Two types of insulation and methods were used. Extruded polystyrene boards were placed by hand (the same as at Sudbury) at the desired elevation. Polyurethane was foamed in place by spraying the chemicals on the road bed with a specially constructed self-propelled spraying machine. This paper discusses the relative merits of the different methods of roads and, in a broader context, the protection against freezing of underground utilities, such as water mains and sewers.

A method has been devised for using normal monthly mean temperatures to compute normal freezing and thawing degree- days in change-over months with adequate accuracy. The tedious calculation of daily departures from freezing for 30 years can, therefore, be avoided. The method has been applied to over 800 Canadian stations and the resulting freezing and thawing indices used to prepare the charts accompanying this note.

Heave and moisture intake and explusion were measured in four soil samples at different overburden pressures from 0.5 to 4 kg/cm². A step change in temperature, a requirement of the procedure, was imposed at one end of the sample, which was originally at a uniform temperature, to induce unidirectional freezing in a specially-designed test cell. Soils were medium in texture and had obtained along the proposed Mackenzie HIghway, N.W.T. The response to pressure and freezing conditions imposed were similar for all soils. Of particular note was the constancy in the heave rate throughout each test. At high pressures, water was expelled from the sample initially, but in all cases this was followed by water intake after the rate of frost penetration had decreased.

One of the typical features of the frost heaving phenomenon described i the authors' paper is that the total heave rate is essentially constant for any particular overburden pressure and cold side temperature. The fact that a large change in rate of frost penetration occurs after the step change in temperature in the cold side has been imposed indicates that the rate of frost penetration does not have a significant effect on the total heave rate.

The results of a 3-year insulated road study showed that frost penetration inward from the edge of an insulated area is about the same as the downward penetration on a control section. Moisture accumulated in the frost-susceptible subgrade after the frost line penetrated the insulation. During periods of rapid cooling, the temperature of the surface above an insulated pavement may be lowered sufficiently to permit surface icing if atmospheric moisture conditions are suitable. Terminating the insulation without feathering induces abrupt changes in elevation in the roadway as a result of heaving.

Insulating house basements is becoming a popular method of reducing space heating energy consumption and improving the basement environment. With a reduced heat flow to the surrounding soil, the soil temperatures are lowered and the depth of the frost penetration increases. Insulation strategies must be considered carefully, otherwise foundations bearing on soils that experience volume changes upon freezing can be shifted and building damage may occur. This study reports on frost penetration measurements adjacent to nine different house basement configurations. The maximum depth of frost penetration against the exterior wall and 1.5 m (5 ft.) from the wall are reported for a number of winters with a range of freezing indices from 1249 degrees C days to 2409 degrees C days (2248 degrees F days to 4336 degrees F days). Initial observations show that only shallow, highly insulated basements with both wall and floor insulation have frost depths extending below the footings.

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.

Concerning the influence of overburden pressure on the relation between rate of heave and cold-side temperature, studies show that the heave rate for various overburden pressures tends to converge as the cold-side temperature is lowered, and the maximum rates of ice accumulation at low pressures occur at temperatures closer to 0°C than do those at high pressures. Evidence is also presented that a heaving zone is involved in frost action rather than a freezing plane. This zone extends over an increasingly greater temperature range and distance as the overburden pressure is increased. Using the concept of a heaving zone leads to a method for calculating the heave-decrease curve. The period of heave decrease is marked by a rapidly increasing ice segregation ratio and a reduced frostpenetration rate.

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 study was concerned with determining the effect of rate of freezing on frost action under laboratory conditions. This was done for the saturated and near-saturated moisture conditions of the soil. The rate of freezing was measured both in terms of heat flow and rate of frost penetration. Three soils of widely differing properties were used to bring out major differences in behavior to freezing. The results show a positive relation between net heat flow or frost penetration rate and heaving rate. Increasing the rate of heat flow away from the freezing plane in all cases increased the rate of moisture flow to the freezing plane and consequently also the heaving rate. This was shown to be true for the three soils studied at high moisture contents. It is not correct to compare the frost susceptibility of different soils in laboratory freezing experiments on the basis of equal rates of frost penetration when, in fact, this does not occur in the field. The rate of heat extraction used in laboratory tests of frost heaving should be related to the actual heat flow in the environment of the soil. The results presented should be useful in setting up practical laboratory freezing procedures for the realistic evaluation of the frost susceptibility of soils in the field.

Observations on which this report is based were made in the period 1962-66. They were made in natural soil and water- main trenches and were done to establish methods of determining depth of frost penetration, paying special attention to the question of depth, of soil cover over water and sewer mains to prevent freezing. Observations were carried out at 21 stations using special probes at different depths to measure temperature and thermal conductivity, both in bare and snow covered areas. Field observations were used to verify calculation methods. A calculation method was used to determine the frost penetration for five different types of soil at varying mean annual temperatures and minimum winter temperatures. Observations showed that the heat insulating capacity of snow is less than could be expected from its thermal conductivity, mostly because the structure of the snow is continually changing. Therefore an equivalent conductivity was used which depends on the mean annual temperature. Special treatment was given to the depth of soil required over water-mains, which allows for the heating effect of the water carried in the pipes. For the frost protection of service pipes to buildings a practical method suggested is to use electrical heating to compensate for heat losses. The calculated frost penetration method compared well with actual measurements.

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.

This Digest contains a brief description of the physical processes involved in ground freezing and frost heaving and some suggestions on ways to prevent or diminish frost damage to various structures.

The effect of frost on a prestressed tie-back system of excavation bracing is described. Measurements of the horizontal movement of the wall as well as the changes in the prestressing force in the tendons, were made during the winter of 1965-66. These indicated that although considerable frost pressures did exist, the tendon loads were lower than had been anticipated owing to plastic flow creep in the bracing system. Suggestions for future installations were made.

On trouvera dans le présent Digeste une brève description des processus physiques impliqués dans la congélation du sol et dans le soulèvement par le gel ainsi que des suggestions concernant les moyens à employer pour empêcher ou diminuer les dommages causés aux ouvrages par le gel.

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.

This paper presents one winter's results of two 100-ft city pavement sections insulated with a 2-in. thickness of extruded polystyrene plastic foam in Sudbury, Ontario, Canada. The experimental results consisted of temperature measurements, frost-depth measurements with methylene blue gages, elevation measurements for frost heave and Benkelman beam deflections following the thawing period. The insulation reduced frost penetration by 35 in. during a 2600 degree-day winter. Thermoconductivity measurements showed that no deterioration occurred in the insulating properties of the insulation. Frost penetration in the control area was approximately 65 in., which compared favorably with the depth predicted by the U.S. Army Corps of Engineers from measurements in granular base course beneath snow-cleared airport runways.

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

Emulsion paints have been widely promoted on the basis of their ability to "breathe" or transmit water vapour. In Canada, their chief use has been on concrete structures. However, in localities where stucco is used, there may be a desire to apply emulsion paints for decorative purposes. Concern has been expressed that their use might lead to spalling of the rendering surface because of repeated freezing and thawing cycles. The work reported here shows that application of emulsion paints to old rendering is satisfactory. If applied to fresh rendering, damage from frost action may occur if cement is not included in the formula. Emulsion paints cannot be expected to waterproof masonry walls that were improperly constructed in the first place.

Present theory of frost action in cement is re-examined in the light of the results of recent experiments (dimensional changes, adsorption characteristics, calorimetry, DTA). It is found that hydrostatic pressure in cement is not generated by the 9 per cent difference between the specific volume of water and ice but by the changed interaction between the cement and the adsorbed water on its solidification. The proposed mechanism raises the possibility that new methods for frost protection may be developed. Similarly, frost susceptibility may be tested in a more reliable way.