Laboratory Study on Frost Heave of Ballast

Abstract

Frost heave is a long-recognized issue contributing to the railway track upheaval in cold regions. Generally, frost heave is believed to happen in the subgrade layer of transportation infrastructure, referred to as the volume expansion of frozen soils, which are susceptible to frost action with the presence of moisture. The aggregate layer, such as highway base course or railroad ballast, is believed not to be prone to the frost heave due to its large void ratio and low capability to hold moisture content. However, recent reports around the world, such as Norway, USA, China, and Japan, etc., indicate the frost heave does happen in the ballast layer even when the moisture content is low. Existing literatures, which often believe track upheaval should not happen on aggregate like ballast, cannot well explain the recently observed phenomenon. In this study, the researchers conduct a series of laboratory experiments aiming to identify the possible reason that cause ballast frost heave in a well-controlled environment. Clean ballast is prepared with different moisture conditions, including half submerged condition and fully submerged condition. The growth of ice and movement of particles are tracked and qualified through image analysis. The findings from this study provide evidence to prove the effect of ice formation on ballast and would help to explain the root cause of ballast frost heave.