Influence of overconsolidation on the freezing characteristics of a clayey silt

1989 ◽  
Vol 26 (1) ◽  
pp. 9-21 ◽  
Author(s):  
J.-M. Konrad
Keyword(s):  
Hydraulic Conductivity ◽  
Void Ratio ◽  
Moisture Transfer ◽  
Frozen Soil ◽  
Frost Heave ◽  
Unfrozen Water ◽  
Initial Void Ratio ◽  
Clayey Silt ◽  
Segregation Potential ◽  
Lens Formation

Laboratory freezing tests were performed on a saturated clayey silt at various overconsolidation ratios (OCR) to establish the relationship between initial void ratio and stress history, and the amount of moisture transfer during freezing. The frost heave tests were analysed in terms of the segregation potential as well as a function of the temperature of ice lens formation and the overall hydraulic conductivity of the frozen fringe. All other factors being the same, the segregation potential was found to increase with increasing values of OCR (decreasing initial void ratios). However, the combined effects of decreasing void ratio and increasing suction at the frost line, all other factors being identical in all freezing tests, resulted in decreasing segregation potentials. This trend was the result of a decrease in the temperature of ice lens formation and the concomitant decrease in overall hydraulic conductivity of the frozen fringe. A simple model showed that the capillary unfrozen water between clay particles increases when the particles pack closer together, as overconsolidation increases, allowing the migratory water to freeze within the frozen soil at a colder temperature. Key words: frost heave, clayey silt, overconsolidation, void ratio.

Segregation potential – pressure – salinity relationships near thermal steady state for a clayey silt

1990 ◽  
Vol 27 (2) ◽  
pp. 203-215 ◽  
Author(s):  
J.-M. Konrad
Keyword(s):  
Steady State ◽  
Pore Water ◽  
Moisture Transfer ◽  
Frost Heave ◽  
Water Salinity ◽  
Saline Soils ◽  
Clayey Silt ◽  
Segregation Potential ◽  
Pore Water Salinity ◽  
Thermal Steady State

Laboratory freezing tests were performed on a saturated clayey silt at various pore-water salinities and applied pressures to establish the relationships between pore-water salinity, overburden, and the amount of moisture transfer during freezing near thermal steady state conditions. The experimental data confirmed that the concept of segregation potential established for salt-free soils can be extended to saline soils. The segregation potential at the onset of the final ice lens in step-freezing tests (or near thermal steady state) should be related to the average salinity of the frozen fringe associated with the final ice lens. This pore-water salinity is different from the initial pore-water salinity as a result of solute exclusion at the ice lenses causing an enrichment as freezing proceeds. Unfortunately, it is very difficult to determine the average salinity in the frozen fringe owing to its small size. Instead, it is proposed to use the initial water salinity to develop the constitutive equations in freezing saline soils. A procedure for frost heave predictions in the field is outlined. Key words: freezing tests, clayey silt, saline water, frost heave.

scholarly journals The Modelling of Freezing Process in Saturated Soil Based on the Thermal-Hydro-Mechanical Multi-Physics Field Coupling Theory

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2684
Author(s):  
Dawei Lei ◽  
Yugui Yang ◽  
Chengzheng Cai ◽  
Yong Chen ◽  
Songhe Wang
Keyword(s):  
Thermal Conductivity ◽  
Hydraulic Conductivity ◽  
Void Ratio ◽  
Soil Column ◽  
Soil Freezing ◽  
Frost Heave ◽  
Freezing Process ◽  
Soil Particles ◽  
Initial Void Ratio ◽  
Freezing Depth

The freezing process of saturated soil is studied under the condition of water replenishment. The process of soil freezing was simulated based on the theory of the energy and mass conservation equations and the equation of mechanical equilibrium. The accuracy of the model was verified by comparison with the experimental results of soil freezing. One-side freezing of a saturated 10-cm-high soil column in an open system with different parameters was simulated, and the effects of the initial void ratio, hydraulic conductivity, and thermal conductivity of soil particles on soil frost heave, freezing depth, and ice lenses distribution during soil freezing were explored. During the freezing process, water migrates from the warm end to the frozen fringe under the actions of the temperature gradient and pore pressure. During the initial period of freezing, the frozen front quickly moves downward, the freezing depth is about 5 cm after freezing for 30 h, and the final freezing depth remains about 6 cm. The freezing depth of the soil column is affected by soil porosity and thermal conductivity, but the final freezing depth mainly depends on the temperatures of the top and lower surfaces. The frost heave is mainly related to the amount of water migration. The relationship between the amount of frost heave and the hydraulic conductivity is positively correlated, and the thickness of the stable ice lens is greatly affected by the hydraulic conductivity. With the increase of the hydraulic conductivity and initial void ratio, the formation of ice lenses in the soil become easier. With the increase of the initial void ratio and thermal conductivity of soil particles, the frost heave of the soil column also increases. With high-thermal-conductivity soil, the formation of ice lenses become difficult.

Effect of freeze–thaw cycles on the freezing characteristics of a clayey silt at various overconsolidation ratios

1989 ◽  
Vol 26 (2) ◽  
pp. 217-226 ◽  
Author(s):  
J.-M. Konrad
Keyword(s):  
Void Ratio ◽  
Frost Heave ◽  
Freezing And Thawing ◽  
Freeze Thaw ◽  
Maximum Reduction ◽  
Clayey Silt ◽  
Wide Range ◽  
Repeated Freezing ◽  
Segregation Potential ◽  
Overconsolidated Soils

Repeated freezing and thawing affect the structure of clayey silts over a wide range of consolidation ratios. While the overall void ratio of the thawed soil either decreased, as in lightly overconsolidated soils, or increased, as in heavily overconsolidated samples, freezing and thawing caused a reduction in segregation potential after each freeze–thaw event. All the changes occurred during the first three cycles. The maximum reduction in segregation potential was about 50% in all samples. The implications for frost heave predictions in the field are discussed. Key words: freeze–thaw, clayey silt, segregation potential, frost heave.

Discrete ice lens theory for frost heave in soils

1991 ◽  
Vol 28 (6) ◽  
pp. 843-859 ◽  
Author(s):  
J. F. (Derick) Nixon
Keyword(s):  
Hydraulic Conductivity ◽  
Temperature Gradient ◽  
Frozen Soil ◽  
Soil Freezing ◽  
Frost Heave ◽  
Overburden Pressure ◽  
Discrete Location ◽  
Freezing Soil ◽  
Analytical Technique ◽  
Segregation Potential

The existing segregation potential (SP) method for frost heave prediction in soils is semiempirical in nature and does not explicitly predict the relationship between heave rate, temperature gradient, and other more fundamental soil properties. The SP method assumes that the heave rate is directly related to the temperature gradient at the frost front but acknowledges that the SP parameter is dependent on pressure, suction at the frost front, cooling rate, soil type, and so forth. This paper extends and modifies an approximate analytical technique of Gilpin and accounts for the effects of distributed phase change within the freezing fringe in both the head- and mass-transfer components of the formulation. The approach requires as input a relationship between frozen hydraulic conductivity and temperature and predicts the discrete location of each ice lens within the freezing soil. The solution can be carried out quickly on a microcomputer to obtain the heave, suction at the frost front, ice lens temperature, and other results of interest with time. Furthermore, the discrete ice lens method predicts the effects of changing overburden pressure on the predicted heave rate. A method of extracting input parameters for the discrete ice lens procedure from a series of frost heave tests is proposed. The discrete ice theory has been tested and calibrated against well-documented frost heave test results in the literature, and very encouraging agreement between prediction and observation has been obtained. Key words: frost heave, discrete ice lens, segregation potential, hydraulic conductivity of frozen soil, freezing soil.

Stress Analysis of Pipeline Subjected to Differential Frost Heave

2013 ◽  
Author(s):  
Yan Di ◽  
Jian Shuai ◽  
Lingzhen Kong ◽  
Xiayi Zhou
Keyword(s):  
Strain Analysis ◽  
Element Model ◽  
Frozen Soil ◽  
Computational Method ◽  
Frost Heave ◽  
Safe Operation ◽  
Stress Strain ◽  
Segregation Potential ◽  
Differential Frost Heave ◽  
Design Construction

Frost heave must be considered in cases where pipelines are laid in permafrost in order to protect the pipelines from overstress and to maintain the safe operation. In this paper, a finite element model for stress/strain analysis in a pipeline subjected to differential frost heave was presented, in which the amount of frost heave is calculated using a segregation potential model and considering creep effects of the frozen soil. In addition, a computational method for the temperature field around a pipeline was proposed so that the frozen depth and temperature variation gradient could be obtained. Using the procedure proposed in this paper, stress/strain can be calculated according to the temperature on the surface of soil and in a pipeline. The result shows the characteristics of deformation and loading of a pipeline subjected to differential frost heave. In general, the methods and results in this paper can provide a reference for the design, construction and operation of pipelines in permafrost areas.

Ice lens formation at a silt–sand interface

1995 ◽  
Vol 32 (3) ◽  
pp. 488-495 ◽  
Author(s):  
Sharon L. Smith ◽  
Peter J. Williams
Keyword(s):  
Soil Structure ◽  
Frozen Soil ◽  
Frost Heave ◽  
Controlled Environment ◽  
Freezing And Thawing ◽  
Ground Freezing ◽  
Residual Deformations ◽  
Cumulative Residual ◽  
Lens Formation ◽  
Soil Interface

A major experiment simulating ground freezing around a buried chilled pipeline in a controlled-environment facility provided an opportunity to examine the form and orientation of ice lenses associated with a vertical interface between silt and sand. The heave of the silt decreased towards the interface and ice lenses in the silt were found to dip at an increasing angle in the same direction. Consideration of the thermal regime suggests that the direction of heat flow influences the orientation of the lenses. The interface was irregular and ice lenses at the lower part of the interface were closely aligned to it, indicating that changes in soil texture also influence ice lens orientation. Deformation of ice lenses appears to have occurred in the silt near to the interface. The arrangement of the lenses can be explained by the different thermal properties and thermodynamic behaviour of the two materials and by the mechanical "anchorage" of the sand in which there is no ice lens formation. Cycles of freezing and thawing modify soil structure and produce cumulative residual deformations which are modified by a soil interface. Key words : frost heave, ice lenses, frozen soil, vertical silt–sand interface, chilled pipeline, differential heave.

Sixteenth Canadian Geotechnical Colloquium: Frost heave in soils: concepts and engineering

1994 ◽  
Vol 31 (2) ◽  
pp. 223-245 ◽  
Author(s):  
J.-M. Konrad
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Point Of View ◽  
Frost Heave ◽  
Fundamental Point ◽  
New Concepts ◽  
Segregation Potential ◽  
Thermal Histories ◽  
Ice Content ◽  
Lens Formation

Frost heave in soils is analysed from a fundamental point of view to predict the development of periodic ice lens formation that is observed in frozen soils. A model of simultaneous heat and mass transfer associated with three new concepts is described and was found to exhibit many of the frost heave features observed in laboratory tests. An efficient frost heave parameter termed the segregation potential, SP, is also described and found to be an adequate input to a general formulation of heat and mass transfer for the prediction of frost heave in soils for both laboratory and field conditions. Representative values of SP depend on the stress and thermal histories of the soil deposit. The SP-based approach can be used for solving two-dimensional frost heave problems and yields stress, temperature, and ice-content distributions with time. Key words : frost heave, soils, segregation potential, simulation, thermodynamics.

scholarly journals Frost Heave due to Ice Lens Formation in Freezing Soils

1995 ◽  
Vol 26 (2) ◽  
pp. 125-146 ◽  
Author(s):  
D. Sheng ◽  
K. Axelsson ◽  
S. Knutsson
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Frost Heave ◽  
Darcy Law ◽  
Unfrozen Water ◽  
Clapeyron Equation ◽  
Unfrozen Water Content ◽  
Steady State Heat ◽  
Ice Pressure ◽  
Lens Formation

A frost heave model which simulates formation of ice lenses is developed for saturated salt-free soils. Quasi-steady state heat and mass flow is considered. Special attention is paid to the transmitted zone, i.e. the frozen fringe. The permeability of the frozen fringe is assumed to vary exponentially as a function of temperature. The rates of water flow in the frozen fringe and in the unfrozen soil are assumed to be constant in space but vary with time. The pore water pressure in the frozen fringe is integrated from the Darcy law. The ice pressure in the frozen fringe is determined by the generalized Clapeyron equation. A new ice lens is assumed to form in the frozen fringe when and where the effective stress approaches zero. The neutral stress is determined as a simple function of the unfrozen water content and porosity. The model is implemented on an personal computer. The simulated heave amounts and heaving rates are compared with experimental data, which shows that the model generally gives reasonable estimation.

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