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BVFF nummer:
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2018:1-11
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Projekttitel
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Differential frost heave modeling
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Projektledare/Kontaktperson
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Tommy Edeskär
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Telefon
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0920-493065
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Utförarorganisation
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LTU
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Medutförare
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Jan Laue, Professor, LTU tel 0920-491288, e-post jan.laue@ltu.se, Luleå tekniska universitet, 971 87 Luleå
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Bakgrund
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Frost heave is a major distress factor for infrastructure in Sweden and other cold regions. Current practice in frost heave design is either to undertake measures to avoid frost penetration in the subgrade or estimate the frost heave in one dimension. The drawback of the latter method is that uniform frost heave ideally does not affect the infrastructure much. Differential frost heave on the other hand causes pavement to crack, increases pavement roughness and decrease the track alignment.
To be able to expand current one-dimensional frost heave approaches to at least two-dimensions, the physical process of formation of segregational ice lenses needs to be addressed. A simple approach is to approximate differential heave by semi-one-dimensional incremental heave estimation. A more physical consistent approach is to describe this; focus is given to the suction created upon freezing. Suction and water flow is possible to model in two- or three dimension in soils. The ability of a soil to generate suction during the formation of ice lenses could be describes by geotechnical properties and boundary conditions. These prerequisites and generated suction could be determined in laboratory tests.
Two dimensional heave modeling results could be applied in maintenance actions to mitigate longitude pavement cracking and in pavement design to estimate strains in the pavement layer caused by frost heave.
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Sammanfattning
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Today’s approach in frost heave modeling is 1-dimensional, focusing on maximal heave or heave rate both related to uniform frost heave. This has minor effect on pavement performance as differential heave causes pavement cracking and increased roughness. One approach to model the differential heave is to focus on the suction created during formation of segregational ice. Suction and access to water is possible to model in two or three dimensions if the thickness and horizontal extension of ice-lenses can be estimated. The 2D-heave model could be utilized e.g. to determine when to execute snow removal in ditches to mitigate the longitude cracking of pavements. The suction might also be a crucial parameter in defining frost susceptibility.
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Förväntat resultat
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Fundamental contributions of describing the heave process. The first model attempts of differential frost heave modeling in 2D. If the approach is successful the concept could serve as measure of the potential of differential heave of different soils and a basic modeling approach of heave around specific structures such as culverts and bridges.
The model can be utilized to determine maintenance strategies when to remove the snow in the ditches to mitigate differential cross sectional heave, the major cause of longitude cracking.
By studying a cross section of a road during winter time it would be possible to model how to adjust the frost front by snow removal in the open ditches to mitigate the differential heave in the pavement profile.
There is also a potential in the longitude direction in comparing the re-occurrence of ice-lenses by road profiling and wave length analysis and correlate this to the subgrade soil ability to form ice lenses in the extension of the horizontal plane as additional pavement evaluation.
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Plan för resultatspridning och implementering
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The results will be spread within the scientific community by journal papers and conference proceedings. Preliminary three journal papers are planned; results from the one-dimensional suction tests, results from the multidimensional scaled box-tests and a modeling paper on mitigation of longitude pavement cracks. The work is planned to be presented on the international conferences ICOP 2020 and BCRRA 2021.The modeling results could be implemented in the winter maintenance guidelines aimed for the maintenance division staff at Trafikverket and the contractors. The findings will be discussed within TC 216 in ISSGME. The licentiate and PhD-thesis will be public available at the LTU web-site.
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Tidsramar
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2018-03-01 – 2023-12-31
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