When the temperature drops below zero degrees, phase change from water to ice causes a volume expansion of 9 %. Under the same temperature conditions, volumetric expansion of soil occurs not only by freezing of pore water but also by ice segregation. The Republic of Korea is classified as a seasonal frozen area because freezing and thawing at shallow depth of ground surface happen from the winter to spring seasons. If freezing and thawing are repeated, unexpected deformation of civil engineering structures occurs and, sometimes, critical structural instability results in destruction. In this paper, in order to observe frost heave phenomenon, laboratory testing apparatus are presented including a newly developed temperature-controllable cell. Also, frost heave tests are carried out using artificial soils to investigate the effect of fine-erained soils on frost heave.
When fine-grained soils are subjected to freezing, frost heave occurs because of ice lens formation, which is a representative characteristic of frost heave in soils. Konrad and Morgenstern(1980, 1981) researched a mechanistic theory of ice lens formation and proposed a segregation potential theory using water intake rate as a parameter to solve problems caused by the formation of an ice lens. After that, Konrad and Morgenstern(1982), Fukuda and Kinosita(1985), Penner(1986), Konrad(1987, 1988, 2005), and Yuzuru(1993) researched segregation potential theory. Laboratory testing is the most direct method to determine the characteristics of segregation potential theory. In this paper, we carried out laboratory frost heave tests using a temperature-controllable cell, which is also able to measure water intake amount with elapsed time.
As shown in Figure 1, we used a cell that can individually control the upper, bottom, and periphery temperatures, and a hydraulic system that can measure water intake rate. Table 1 summarizes the typical characteristics of the frost heave testing system. The freezing type is unidirectional, which can be set from top to bottom (in the upward direction) or in the opposite direction (in the downward direction). Drainage conditions can be set as drained (open system) or undrained (closed system), and water is drawn or expelled through drainage lines connected to the upper and bottom pedestals. The cell, made using acrylic, controls the temperature using a transparent anti-freezing liquid, which makes it possible to observe the formation of ice segregation. The dimensions of the specimens are 100 mm diameter and 100 mm height.
