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Water flow and heat transport in frozen soil: Numerical solution and freeze-thaw applications
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
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2004 (English)In: Vadose Zone Journal, ISSN 1539-1663, E-ISSN 1539-1663, Vol. 3, no 2, 693-704 p.Article in journal (Refereed) Published
Abstract [en]

A new method is presented to account for phase changes in a fully implicit numerical model for coupled heat transport and variably saturated water flow involving conditions both above and below zero temperature. The method is based on a mixed formulation for both water flow and heat transport similar to the approach commonly used for the Richards equation. The approach enabled numerically stable, energy- and mass-conservative solutions. The model was evaluated by comparing predictions with data from laboratory column freezing experiments. These experiments involved 20-cm long soil columns with an internal diameter of 8 cm that were exposed at the top to a circulating fluid with a temperature of −6°C. Water and soil in the columns froze from the top down during the experiment, with the freezing process inducing significant water redistribution within the soil. A new function is proposed to better describe the dependency of the thermal conductivity on the ice and water contents of frozen soils. Predicted values of the total water content compared well with measured values. The model proved to be numerically stable also for a hypothetical road problem involving simultaneous heat transport and water flow. The problem was simulated using measured values of the surface temperature for the duration of almost 1 yr. Since the road was snow-plowed during winter, surface temperatures varied more rapidly, and reached much lower values, than would have been the case under a natural snow cover. The numerical experiments demonstrate the ability of the code to cope with rapidly changing boundary conditions and very nonlinear water content and pressure head distributions in the soil profile.

Place, publisher, year, edition, pages
2004. Vol. 3, no 2, 693-704 p.
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-92713DOI: 10.2136/vzj2004.0693ISI: 000227468800035OAI: oai:DiVA.org:uu-92713DiVA: diva2:165891
Available from: 2005-03-11 Created: 2005-03-11 Last updated: 2013-04-09Bibliographically approved
In thesis
1. Water and Heat Transport in Road Structures: Development of Mechanistic Models
Open this publication in new window or tab >>Water and Heat Transport in Road Structures: Development of Mechanistic Models
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The coupled transport of water and heat, involving freezing and thawing, in the road structure and its immediate environment is important to consider for optimal design and maintenance of roads and when assessing solute transport, of e.g. de-icing salt, from roads. The objective of this study was to develop mechanistic models, and measurement techniques, suitable to describe and understand water flow and heat flux in road structures exposed to a cold climate.

Freezing and thawing was accounted for by implementing new routines in two numerical models (HYDRUS1D/2D). The sensitivity of the model output to changes in parameter values and operational hydrological data was investigated by uncertainty and sensitivity analyses. The effect of rainfall event characteristics and asphalt fractures on the subsurface flow pattern was investigated by scenario modelling. The performance of water content reflectometers (WCR), measuring water content, was evaluated using measurements in two road structure materials. A numerical model was used to simulate WCR sensor response. The freezing/thawing routines were stable and provided results in agreement with laboratory measurements. Frost depth, thawing period, and freezing-induced water redistribution in a model road was greatly affected by groundwater level and type of subgrade. The simulated subsurface flow patterns corresponded well with published field observations. A new method was successful in enabling the application of time domain reflectometer (TDR) calibration equations to WCR output. The observed distortion in sampling volume for one of the road materials could be explained by the WCR sensor numerical model. Soil physical, hydrological, and hydraulic modules proved successful in simulating the coupled transport of water and heat in and on the road structure. It was demonstrated in this thesis that numerical models can improve the interpretation and explanation of measurements. The HYDRUS model was an accurate and pedagogical tool, clearly useful in road design and management.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 69 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 23
Hydrology, Water flow, Heat flow, Unsaturated flow, Freeze-thaw, Numerical models, Uncertainty analysis, Sensitivity analysis, Roads, Overland flow, Flow patterns, TDR, Water content reflectometer, Calibration, Fractures, Hydrologi
National Category
Oceanography, Hydrology, Water Resources
urn:nbn:se:uu:diva-4822 (URN)91-554-6172-7 (ISBN)
Public defence
2005-04-01, Axel Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Available from: 2005-03-11 Created: 2005-03-11Bibliographically approved

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