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Water and Heat Transport in Road Structures: Development of Mechanistic Models
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
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. , p. 69
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 23
Keywords [en]
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
Keywords [sv]
Hydrologi
National Category
Oceanography, Hydrology and Water Resources
Identifiers
URN: urn:nbn:se:uu:diva-4822ISBN: 91-554-6172-7 (print)OAI: oai:DiVA.org:uu-4822DiVA, id: diva2:165895
Public defence
2005-04-01, Axel Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Opponent
Supervisors
Available from: 2005-03-11 Created: 2005-03-11 Last updated: 2018-01-13Bibliographically approved
List of papers
1. Water flow and heat transport in frozen soil: Numerical solution and freeze-thaw applications
Open this publication in new window or tab >>Water flow and heat transport in frozen soil: Numerical solution and freeze-thaw applications
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2004 (English)In: Vadose Zone Journal, ISSN 1539-1663, E-ISSN 1539-1663, Vol. 3, no 2, p. 693-704Article 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.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-92713 (URN)10.2136/vzj2004.0693 (DOI)000227468800035 ()
Available from: 2005-03-11 Created: 2005-03-11 Last updated: 2017-12-14Bibliographically approved
2. Equifinality and sensitivity in freezing and thawing simulations of laboratory and in situ data
Open this publication in new window or tab >>Equifinality and sensitivity in freezing and thawing simulations of laboratory and in situ data
2006 (English)In: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 44, no 1, p. 20-37Article in journal (Refereed) Published
Abstract [en]

Numerical models of soil freezing and thawing are being increasingly used in, e.g., agriculture, forestry, ecology and civil engineering. This study was conducted to 1) elucidate the sensitivity in simulation output to the variability of model parameters for the hydrodynamic model Hydrus-1D and 2) investigate how two operational considerations in the model setup, groundwater level and subgrade material (soil texture), affect indicators of road accessibility in northern Sweden. The analysis was carried out by applying the generalized likelihood uncertainty estimation (GLUE) procedure when simulating laboratory measurements of freezing cylinders and by a more conventional sensitivity analysis, varying one parameter at a time, using road surface temperatures measured during nearly 1 year as upper boundary condition. For the simulation of the laboratory experiment, it was found that, although the thermal conductivity scaling factor, λf, and the convective heat transfer coefficient, hc, most strongly affected the output, no parameter was redundant for the given problem. The frost depth was most sensitive to changes in λf and hc, while the water content in the unfrozen zone was most sensitive to changes in the hydraulic conductivity impedence parameter Ω. For the 1-year road simulation, the frost depth was larger for sand than for the loam and silt subgrades; the thawing period was shortest for sand and longest for the silt subgrade; and the silt subgrade allowed for the largest frost-induced upward water flow. Thus, among the subgrades studied, roads built on silt show the potential of being most frost-susceptible as a consequence of having the largest elevated water content in combination with the longest time of thawing. The study performed indicates that the model can provide information of interest from an operational perspective, allowing for local predictions important in the road construction and maintenance process.

Keywords
soil freezing, highways, sensitivity analysis, numerical models
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-92714 (URN)10.1016/j.coldregions.2005.06.004 (DOI)000234534400003 ()
Available from: 2005-03-11 Created: 2005-03-11 Last updated: 2017-12-14Bibliographically approved
3. Modeling water flow patterns in flexible pavements
Open this publication in new window or tab >>Modeling water flow patterns in flexible pavements
2005 (English)In: Journal of the Transportation Research Board, ISSN 0361-1981, Vol. 1936, p. 131-141Article in journal (Refereed) Published
Abstract [en]

Most road design models do not explicitly account for moisture transport mechanisms in roads, even though it is well known that water content plays an important part in the deterioration of roads. The Swedish National Road Administration aims to improve the current situation by supporting the development of models that eventually can provide a better and more complete description of the road and environment system. The applicability of hydrological theories and methods to the road and environment system was investigated. Particular attention was paid to flow patterns inside the road as affected by capillary barriers and generated by mechanisms of surface runoff, followed by infiltration into cracks, and the embankment. Particle tracking was used to investigate the effect of rain intensity, precipitated amount, or fracture conductivity on the flow patterns. Changes in rain intensity had a small effect on flow patterns, but velocities were higher for larger rain intensities. Both changes in precipitated amount and fracture conductivity controlled the appearance of the flow patterns, but capillary barrier effects were limited. The numerical code used proved to be mostly appropriate in describing the relevant processes.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-92715 (URN)10.3141/1936-16 (DOI)
Available from: 2005-03-11 Created: 2005-03-11 Last updated: 2013-02-08Bibliographically approved
4. Water content reflectometer for coarse materials: application to construction materials and effect of sampling volume
Open this publication in new window or tab >>Water content reflectometer for coarse materials: application to construction materials and effect of sampling volume
(English)In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973Article in journal (Refereed) Submitted
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-92716 (URN)
Available from: 2005-03-11 Created: 2005-03-11 Last updated: 2017-12-14Bibliographically approved

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