Abstract: Based on one-dimensional freezing test at five different top cooling temperatures in an open system, the freezing behaviors of the saturated Qinghai-Tibet silty clay are studied experimentally. Combining with digital image acquisition technology and routine data measure system in laboratory, the temperature distribution and development, cryostructure profile development, frost heave development, water supplement process and water content profile are analyzed during one-dimensional freezing of soil sample. Some conclusions are drawn as follows. Firstly, the freezing front in sample reaches a stable state after 26 hours. After that, the longitudinal cryostructure of soil samples can be divided into four belts, including tiny thin layer structural belt, thin layer structural belt, thick layer structural belt and overall structure belt from the cold end to warm end. The frost heave development contains three stages, i. e. fast frost heave stage, stable frost heave stage and linear frost heave stage. The ice lens segregation at the bottom of thin layer structural belt and thick layer structural belt are the main source of frost heave. After tests, the water content profiles of the soil sample indicate that the water content increases in frozen part and decreases in unfrozen part. Meanwhile, the layers in which having the highest water content are located at the location of thick ice lenses. Because of the consolidation of the unfrozen part and water migration from unfrozen part to freezing front and frozen part, the water content of the unfrozen part has decreased and induced a drying phenomenon. The conclusions have provided the dynamic processes of the development of cryostructure and frost heave of the Qinghai-Tibet silty clay under one-dimensional freezing. It is expected that this study will provide a test basis for future study of more reasonable frost heave models.

Key words: one-dimensional freezing test, digital image acquisition technology, cryostructure, frost heave, water migration