Frost Heaving and Induced Pressure of Unsaturated Interfacial Zone between Gravel Ballast and Subgrade

Jinung Do

doi:10.3390/app12062811

Abstract

Most existing railroads are composed of gravel ballast. One of the major issues with gravel ballast is frost damage in cold regions. Gravelly soils are known to be not prone to frost action due to their low water retention capacity and high hydraulic conductivity. However, reports indicated continued frost damages resulting from the mixed zone between gravel ballast and subgrade. This study evaluated the frost heaving and induced pressure of gravel ballast–subgrade soil mixtures via 1D soil column testing in a cold chamber. Gravel ballast and subgrade soil were collected from the railroad in situ. Various mixing ratios and degrees of saturation were used as factors affecting the frost experiments. The mixtures were placed in the cold chamber, and vertical displacements and pressures were measured. Overall evaluations showed that gravelly soils are not a geomaterial prone to frost damage; however, the frost potential of gravel ballast increases as the degree of saturation and the mixing portion of the subgrade soil increase. Therefore, the interfacial zone between gravel ballast and subgrade soil, especially where possible mixing with low drainage exists, needs cautions of potential frost damage.

Highlights

A ballast in railroad tracks is a component that fixes ties in a specific position and distributes the loads transmitted from the ties to the subgrade
This study focuses onon thethe frost action ofmixing unsaturated gravel ballast mixed with ballast–subgrade soil mixtures with various ratios were prepared
This study focuses frost action of unsaturated gravel ballast mixed with subgrade soil

Summary

Introduction

A ballast in railroad tracks is a component that fixes ties (or sleepers) in a specific position and distributes the loads transmitted from the ties to the subgrade. Ballasts are classified into two types: gravel ballast and concrete ballast (or slab ballast). Minor types such as sand, Moorum, slag, etc. The typical design of gravel and concrete ballasts and their pros and cons of each are summarized in recently constructed concrete ballasts are superior, the problem is that most existing railroads are still gravel ballasts. One of the problems with gravel ballasts is the frost heaving in cold regions. In South Korea, Lee et al [6] reported that the number of sites showing frost heaving was 129 with a −4 km distance in 2009, while Han et al [7]

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Conclusion