Effect of Tensile Strength on Ice Lens Initiation Temperature

Abstract

Conditions of ice lens segregation when a new one is start to grow is explored in experimental approach in this paper. Two consecutive open-system frost heave tests have conducted with the same Diluvial Silt of which mean tensile strength is 0.75MPa. Four predominant ice lenses have segregated in 114.2mm high specimen during the first heave test. Then, applying positive temperature to pedestals: i.e. thawing, the second heave test has conducted under the same test condition as the first one. Ice lenses have appeared exactly the same location as the first test. Therefore, it is revealed that ice lens initiation takes place where lower tensile strength remains. The temperature of ice lens initiation during the second frost heave test which have been interpolated by the boundary temperatures have found to be higher than those of the first ones. The difference is almost the same as 0.95 °C. Expected pore ice pressure at the initiation calculated with generalized Clausius-Clapeyron Equation using the temperature difference is 1.05MPa. The calculated pore ice pressure is little higher than the sample tensile strength. Therefore, it is expected that pore ice is pushing structure of mudstone against its tensile strength and overburden pressure to fracture via unfrozen film water.