Experimental study on frost heave characteristics of the PCM-clay under one-dimensional freeze-thaw

The clay incorporated with phase change material (PCM-clay) has the characteristics of freezing resistance and temperature control, which makes it possible to construct clay core walls, channels, embankments, roads and other scenarios with negative temperature. In this paper, according to the environmental characteristics of daily cycle freezing and thawing effect on the construction site in winter, a series of repeated one-dimensional freeze-thaw experiments under short-term, high-frequency and shallow freezing conditions in a closed system are simulated indoors to study the frost heave characteristics of PCM-clay and the law and mechanism of frost heaving development under the action of freezing and thawing cycles. The results show that frost heave characteristics of PCM-clay is improved compared with that of the clay without PCM(pure clay). After freeze-thaw cycles, the final frost heaving amount of phase change clay is far less than that of pure clay under the same freeze-thaw cycles; With the increase of PCM content, the downward moving rate of soil freezing front and the degree of moisture migration decrease; After several freeze-thaw cycles, the cryogenic structure of pure soil has developed more significantly, while PCM-clay does not show obvious frost heave sensitivity, and the formation and development of cryogenic structure are very slow. The analysis shows that the low water content, large porosity, high latent heat energy storage, freezing shrinkage and hydrophobicity of PCM are the main reasons for improving the frost heave characteristics of PCM-clay. This study can provide a theoretical basis for PCM-clay as a construction material for potential dam core walls, channels, embankments, and roads to provide winter construction frost protection in cold regions.