Ice formation in unsaturated frozen soils

This paper presents a procedure for determining unfrozen water saturation in a partially saturated frozen soil (clayey silt) using bulk electrical conductivity (EC) measurements. A modification of Archie’s law is proposed to describe the relationship between soil bulk EC, temperature, porosity and degree of unfrozen water saturation. Compacted samples have been prepared at a dry density around 1.90 Mg/m3 and at dif-ferent degrees of saturation. Samples have been then subjected to freezing paths up to -15 °C. Measurements of bulk EC along the temperature decrease and freezing paths have been used to calibrate parameters associ-ated with the proposed model. These calibrated models allow determining the amount of ice content for a given state of the partially saturated soil (porosity, initial degree of water saturation and temperature). The soil freezing retention curve has been also estimated by combining the Clausius-Clapeyron equation with water retention data on drying. A good agreement has been observed between the estimation based on EC measurements and results from water retention data, which validates the proposed procedure.Postprint (published version

MODELLING SNOWMELT INFILTRATION PROCESSES IN SEASONALLY FROZEN GROUND

In cold regions, freezing and thawing of the soil governs soil hydraulic properties that shape the surface and subsurface hydrological processes. The partitioning of snowmelt into infiltration and runoff has important implications for integrated water resource management and flood risk. However, there is an inadequate representation of the snowmelt infiltration into frozen soils in most land-surface and hydrological models, creating the need for improved models and methods. In this research, we test the Frozen Soil Infiltration Model, FroSIn, which is a novel algorithm for infiltration into the frozen soils. The model is applied in a simple configuration to reproduce observations from field sites in the Canadian prairies, specifically St Denis and Brightwater Creek in Saskatchewan, Canada. We demonstrate the limitations of conventional approaches to simulate infiltration in frozen soils, which systematically over-predict runoff and under predict infiltration. The findings show that FroSIn enables models to predict more reasonable infiltration volumes in frozen soils, and also better represent how infiltration-runoff partitioning is impacted by antecedent soil water content

Bacterial activities in frozen soils

1. By means of the modified synthetic agar plate method bacteria are shown to be present in large numbers in a typical Wisconsin drift soil when it is completely frozen and the temperature is below zero degrees Centigrade; furthermore, increases and decreases in numbers of organisms occur during this period and large numbers are found after the soil has been frozen for a considerable period than before it begins to freeze. 2. During the fall season, the number of bacteria present in the soil diminishes gradually with the lowering of the temperature. 3. Frozen soils possess a much greater ammonifying power than non-frozen soils whether they are tested by the peptone solution method or by the dried blood or cottonseed meal method. 4. During the fall season, the ammonifying power of the soil increases until the temperature of the soil almost reaches zero, when a decrease occurs, and this is followed by a gradual increase and the ammonifying power of the soil reaches a maximum at the end of the frozen period. 5. The nitrifying power of frozen soils is weak and shows no tendency to increase with extension of the frozen period. 6. Frozen soils possess a decided denitrifying power which seems to diminish with the continuance of the frozen period. 7. During the fall season, the denitrifying power of the soil increases until the soil freezes, after which a decrease occurs. 8. Frozen soils possess a nitrogen-fixing power which increases with the continuance of the frozen period, being independent of moderate changes in the moisture conditions but restricted by large decreases in moisture. 9. In the fall, the nitrogen-fixing power of the soil increases until the soil becomes frozen, when it almost ceases, after which a smaller nitrogen-fixing power is established. 10. These results confirm Conn\u27s conclusion that bacteria are alive and multiply in frozen soils. The results of the physiological determinations lend support to his theory of the existence of specific groups of bacteria in the winter which are adapted to growth at low temperatures. 11. The theory is advanced that because of the surface tension exerted by the soil particles on the films of water, the presence of salts in this water, and the concentration in salts which may occur in it when the main body of soil water begins to freeze, it seems justifiable to assume that under average winter conditions, when the soil temperature is not depressed far below zero, the hygroscopic water in soils remains uncongealed and consequently bacteria may live in it and multiply sometimes to a comparatively large extent

Analysis of the methods, means and technologies intensification of earthworks on the frozen soils

В роботі проаналізовано існуючі методи, технології та засоби механізації виконання земляних робіт на мерзлих ґрунтах. Розглянуто основні напрями інтенсифікації цих робочих процесів в обмежених умовах будівництва. Наведено конструктивні рішення робочих органів машин, ресурсо‐ і енергозберігаючі технології та засоби механізації розробки мерзлих ґрунтів.This paper analyzes the existing methods, technologies and means of mechanization of earthworks on the frozen soils. The main directions intensification of these workflows in limited conditions of construction. Presented constructive solutions working bodies of machines, resource‐ and energy‐conserving technologies and mechanization of frozen soils development

Frozen Soil Lateral Resistance for the Seismic Design of Highway Bridge Foundations

INE/AUTC 12.3

Coupled heat and water transport in frozen soils

The effect of freezing on soil temperature and water redistribution was examined in four Mesocosms maintained at different initial water content profiles. An innovative experimental setup involving use of a frozen base layer acting as a proxy to permafrost beneath an active layer made up of packed and undisturbed peat cores was used. The experimental setup was successfully validated for its ability to maintain one dimensional change in temperature and soil water content in frozen soil. There was a substantial amount of water redistribution towards the freezing front, enough to create an impermeable frozen, saturated zone within 15 cm of the soil surface. The water movement was likely due to the potential head gradients between colder and warmer regions created by temperature effects on matric potential of frozen soil. In addition, there is enough evidence that water migration in form of vapour contributed to moisture movement towards the freezing front. Initial moisture profiles appeared to have a significant effect on the freezing induced soil water redistribution likely through differences in moisture dependant hydraulic conductivity. Initial soil moisture profiles also affected the rate of freezing front movement. Frost propagation was controlled by latent heat for long periods, while soil thermal conductivity and heat capacity appeared to control the rate of frost migration once the majority of water was frozen. Using the observations of this study, a conceptual model was proposed to explain freezing of an active layer on a permafrost plateau assuming a variable moisture landscape at onset of winter. Further, a one-dimensional model based on coupled cellular automata approach was developed. The model is based on first order conservation laws to simulate heat and water flow in variably-saturated soil. Inside the model, Buckingham-Darcy’s -and Fourier’s heat laws are used to define the local interactions for water and heat movement respectively. Phase change is brought about by the residual energy after sensible heat removal has dropped the temperature of the system below freezing point. Knowing the amount of water that can freeze, the change in soil temperature is then modeled by integrating along the soil freezing curve. This approach obviates the use of apparent heat capacity term. The 1D model is successfully tested by comparing with analytical and experimental solutions

Geophysical Applications for Arctic/Subarctic Transportation Planning

This report describes a series of geophysical surveys conducted in conjunction with geotechnical investigations carried out by the Alaska Department of Transportation and Public Facilities. The purpose of the study was to evaluate the value of and potential uses for data collected via geophysical techniques with respect to ongoing investigations related to linear infrastructure. One or more techniques, including direct-current resistivity, capacitive-coupled resistivity, and ground-penetrating radar, were evaluated at sites in continuous and discontinuous permafrost zones. Results revealed that resistivity techniques adequately differentiate between frozen and unfrozen ground, and in some instances, were able to identify individual ice wedges in a frozen heterogeneous matrix. Capacitive-coupled resistivity was found to be extremely promising due to its relative mobility as compared with direct-current resistivity. Ground-penetrating radar was shown to be useful for evaluating the factors leading to subsidence in an existing road. Taken as a whole, the study results indicate that supplemental geophysical surveys may add to the quality of a geotechnical investigation by helping to optimize the placement of boreholes. Moreover, such surveys may reduce the overall investigation costs by reducing the number of boreholes required to characterize the subsurface

Comparison of Algorithms and Parameterisations for Infiltration into Organic-Covered Permafrost Soils

Infiltration into frozen and unfrozen soils is critical in hydrology, controlling active layer soil water dynamics and influencing runoff. Few Land Surface Models (LSMs) and Hydrological Models (HMs) have been developed, adapted or tested for frozen conditions and permafrost soils. Considering the vast geographical area influenced by freeze/thaw processes and permafrost, and the rapid environmental change observed worldwide in these regions, a need exists to improve models to better represent their hydrology. In this study, various infiltration algorithms and parameterisation methods, which are commonly employed in current LSMs and HMs were tested against detailed measurements at three sites in Canada’s discontinuous permafrost region with organic soil depths ranging from 0.02 to 3 m. Field data from two consecutive years were used to calibrate and evaluate the infiltration algorithms and parameterisations. Important conclusions include: (1) the single most important factor that controls the infiltration at permafrost sites is ground thaw depth, (2) differences among the simulated infiltration by different algorithms and parameterisations were only found when the ground was frozen or during the initial fast thawing stages, but not after ground thaw reaches a critical depth of 15 to 30 cm, (3) despite similarities in simulated total infiltration after ground thaw reaches the critical depth, the choice of algorithm influenced the distribution of water among the soil layers, and (4) the ice impedance factor for hydraulic conductivity, which is commonly used in LSMs and HMs, may not be necessary once the water potential driven frozen soil parameterisation is employed. Results from this work provide guidelines that can be directly implemented in LSMs and HMs to improve their application in organic covered permafrost soils