DEVELOPMENT OF A TECHNIQUE FOR OBSERVING THE FROST HEAVING PROCESS IN SOIL USING AN INDUSTRIAL MICRO-FOCUS X-RAY CT SCANNER
Keywords:Micro-focus X-ray CT scanner,, Frost Heave, Ice lens, Observation, Density changes
This paper aims at developing a technique for observing the frost heaving process in soil nondestructively and microscopically using an industrial micro-focus X-ray CT scanner. For this purpose, a compact frost heaving apparatus that could freeze the soil in one dimension inside the X-ray CT scanner was developed. This experimental method made it possible to observe the process of ice lens formation in the soil and the shape of the ice lens in detail. In highly frost susceptible weathered volcanic ash, ice lenses like multiple cracks were observed to develop in the early stages of the experiment. When the freezing front was stagnant and the heat was balanced, thick and well-developed ice lenses could be observed. The shape of the ice lens observed in the weathered volcanic ash without gravel was relatively flat. In the terrace deposits containing gravel, ice lenses were observed to be formed from around the larger particles. Furthermore, the formed ice lenses were more uneven in shape than weathered volcanic ash. In the case of volcanic ash sand composed of coarse grains that do not have frost susceptibility, no frost heaving occurred and no ice lenses were observed. The gray levels of the frozen areas of the weathered volcanic ash and terrace deposits with frost susceptibility were found to decrease. This is thought to be because the precipitation of ice lenses in the soil pushed the soil particles apart and reduced their density relatively.