Frost heave causes ground problems such as uneven uplift. In order to prevent geotechnical structures from deforming, engineering design analysis widely adopts the segregation potential (SP). The representative SP can be derived from observations in a thermal steady state condition. However, it is hard to determine when that condition is achieved. In order to obtain a reliable representative SP, this paper proposes a new methodology based on the frost ratio. It is conceptually similar to the degree of consolidation, which is determined by considering excess pore water pressure dissipation, whereas the frost ratio is found by considering thermal diffusion.
When almost-saturated, frost-susceptible soils freeze, frost heave occurs, not only owing to the in-situ freezing of pore water but also to water intake from unfrozen soil or an external source (Seto & Konrad, 1994). Frost action such as frost heave often damages geotechnical structures in regions with seasonal freezing as well as permafrost. It leads to major problems such as uneven uplift or thaw weakening.
Stopping frost heave from deforming geotechnical structures constructed on frozen ground requires engineering knowledge and understanding of the frost heave mechanism. Therefore, many experimental and numerical investigations (Konrad & Morgenstern, 1980; Vinson et al., 1986; Akagawa, 1988; Svec, 1989; Bilodeau et al., 2008; Hendry et al., 2016; Jin et al., 2019a; 2019b; Thomas et al., 2009; Bronfenbrener & Bronfenbrener, 2010; Zheng & Kanie, 2015) have been conducted. Konrad & Morgenstern (1981) proposed a parameter termed segregation potential (SP), which is defined as the ratio of water intake rate (v(t)) and overall temperature gradient (gradT) in a frozen fringe, and has become the most widely accepted parameter for engineering design in frozen ground. Specifically, the representative SP obtained at the onset of the last ice lens formation in a step-freezing laboratory test is widely used for estimating frost susceptibility.
The present study analyzed the effects of freezing mode on the frost heave mechanism. The effect of freezing direction on the determination of representative SP was also considered. Frost heave testing based on the analysis determined the representative SP using a modification of the temperature controllable cell introduced by Jin et al. (2019a) to measure the temperature across a soil specimen. This paper introduces a new parameter, termed the frost ratio, to obtain a reliable and representative SP.