Abstract
Compaction level is an important control index to guarantee subgrade stability. Under freezing‐thawing cycles, water‐heat‐vapor characteristics due to different compaction levels of unsaturated coarse‐grained fillings of high‐speed railway (HSR) subgrade are key factors in understanding the mechanism of freezing‐thawing deformations. Experiments have been performed to study the characteristics of water‐heat‐vapor of coarse‐grained fillings with different compaction levels exposed to freezing and thawing. Fluorescein was used to trace the variations of liquid water in external moisture supply. Test results indicated that compaction level affected the water‐heat‐vapor characteristics of coarse‐grained fillings to some extent. The increase of compaction level increased frost penetration and freezing rate; however, initial water replenishment time delayed during freezing process; liquid water migration height and external liquid migration increased, but total moisture migration, the amount of vapor migration, and vapor of the soil sample moving up to the top pedestal simultaneously reduced. Repeated freezing‐thawing cycles improve the compaction of coarse‐grained fillings. Variation of the amount of moisture caused by the increase of compaction level may decrease the frost heaving of coarse‐grained fillings. Therefore, proper selection and uniformity of compaction level is of critical importance in HSR engineering.
Highlights
Soil compaction is one of the most commonly used methods to ensure the durability and stability of subgrades and foundations in transportation engineering to improve the strength and bearing capacity. e development of road engineering and technical standardizations such as the intelligentization of compaction machinery, California bearing ratio (CBR), and Proctor compaction curves have made soil compaction operations much more convenient than they were before [1]
In 1928–1929, a study in Canada showed that the primary reason of road damages was poor bearing capacity induced by nonuniform compaction of subgrade soil [2]
Influence of Compaction Level on the Variations of Frost Penetration. e comparison of frost penetration and freezing rate during the different freezing processes of soil samples with different compaction levels is shown in Figures 5(a)–5(c), where FF is freezing front and FR
Summary
Soil compaction is one of the most commonly used methods to ensure the durability and stability of subgrades and foundations in transportation engineering to improve the strength and bearing capacity. e development of road engineering and technical standardizations such as the intelligentization of compaction machinery, California bearing ratio (CBR), and Proctor compaction curves have made soil compaction operations much more convenient than they were before [1]. E influence of different compaction levels on liquid water-vapor mixed migration characteristics, temperature field, and final water content of HSR coarsegrained fillings during three freezing and two thawing processes were studied.
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