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Convective Heat Transfer in Crushed Rock Aggregates: The Effects of Grain Size Distribution and Moisture Content

Research output: Contribution to journalArticleScientificpeer-review

Details

Original languageEnglish
Article number04020012
Number of pages11
JournalJOURNAL OF COLD REGIONS ENGINEERING
Volume34
Issue number3
DOIs
Publication statusPublished - 24 Apr 2020
Publication typeA1 Journal article-refereed

Abstract

This study deals with the susceptibility to convective heat transfer of the materials used in the Finnish rail network. Previous studies have found that convection clearly influences the thermal conductivity of coarse aggregates in certain conditions. The occurrence of convection may cause subsoil frost heave. This study investigated the susceptibility of three subballast materials, which were made of different crushed rock aggregates, to convection: railway ballast (31.5/63 mm), subballast layers of crushed rock, and 5/16 mm crushed rock. Convection was found to increase the thermal conductivity of railway ballast severalfold, while the thermal conductivity of the currently used subballast material was also noted to increase clearly when the moving medium contained water. However, no significant increase in thermal conductivity was found in the case of the 5/16 mm crushed rock. Based on these results, it is clear that it is not possible to use tremendously coarse materials in thick structure layers in the northern area. The results of this study were one of the most important factors when the grading recommendation for subballast material used in Finland was changed to include finer material, which clearly reduces the possibility of the onset of convection.

Keywords

  • Natural convection, Frost heave, Railway embankment, Subballast material, Railway ballast

Publication forum classification

Field of science, Statistics Finland