Frost heaving is a discontinuous phenomenon. It starts from rupture in the partially frozen soil called the frozen fringe and then segregation of an ice lens follows in the rupture. Macroscopically, the above-mentioned cycle repeats consistently as soil freezes. The rupture of the frozen fringe should govern the initial conditions of ice lens growth; however, it has not been studied so far. In this paper, the rupture is studied assuming that it has a close relationship with the tensile strength of the frozen fringe. The compressive strength of frozen soil was well-studied in the last century. However, the tensile strength of frozen soil in frozen fringe temperature is discussed along with the unfrozen water content of Dotan and ice tensile strength, and a simplified soil structure model. The tensile strength of the frozen fringe seems to be primarily due to the tensile strength of the pore ice framework.

Segregation freezing, one of the heave mechanisms in freezing soils, is shown to be responsible for the breakdown of freezing welded tuff. Frost heave tests of welded tuff have proved that segregation freezing occurs in rock by revealing ice lens growth, pore water flow and the existence of hydraulic gradient driving water to the freezing front. The physical characteristics of the tuff, such as pore microstructure, mineral composition, unfrozen water conditions, permeability, and so forth, are similar to those of frost‐susceptible soils. An empirical equation, derived from the tuffs water retention curve and unfrozen water content measurements with pulsed NMR, relates the segregation freezing temperature and frost heave pressure. This equation is discussed in the context of the governing thermodynamics. We suggest that the segregation freezing concept is generally applicable to common rocks. La formation de glace de ségrégation, processus bien connu dans le gel des sols est responsable de la fracturation par le gel des tuffs cimentés à chaud. La formation de la glace de ségrégation est démontrée par la croissance de lentilles de glace, l'écoulement de l'eau des pores et l'existence d'un gradient hydraulique amenant l'eau au front de gel.

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