Tensile strength of frozen soil in the temperature range of the frozen fringe

摘要

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 range, i.e. 0 to -2 ℃, has not yet been explored. Disturbed, reconsolidated. and frozen diluvial silt called Dotan in Japan was used as the test specimen. A newly developed tensile test apparatus was used. Fifteen tensile tests were conducted in the temperature range of +0.6 to -1.31 ℃. A steep rise in the tensile strength in the frozen fringe temperature range was observed, being 20 to 70 times higher than that in the unfrozen state. A mechanism of explaining the steep rise in tensile strength 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.