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Equifinality and sensitivity in freezing and thawing simulations of laboratory and in situ data
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.
2006 (English)In: Cold Regions Science and Technology, ISSN 0165-232X, Vol. 44, no 1, 20-37 p.Article 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.

Place, publisher, year, edition, pages
2006. Vol. 44, no 1, 20-37 p.
Keyword [en]
soil freezing, highways, sensitivity analysis, numerical models
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-92714DOI: 10.1016/j.coldregions.2005.06.004ISI: 000234534400003OAI: oai:DiVA.org:uu-92714DiVA: diva2:165892
Available from: 2005-03-11 Created: 2005-03-11 Last updated: 2013-04-23Bibliographically 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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