Abstract: Freezing experiments of remolded clay are made for further study on frost heave characteristics of artificial frozen clay under unidirectional and bidrectional freezing modes and unidirectional condition with a certain amount of headspace separately. The results show that the variations of frost heave force with time are identical under unidirectional and bidrectional freezing modes, but the start time of frost heave under bidrectional freezing mode is slightly earlier than that under unidrectional freezing mode, and the increment speed of frost heave force of bidrectional freezing mode is faster than that of unidrectional freezing mode during the rapid growth stage of frost heave. The frost heave force of the two modes, whose deviations are basically the same at the same temperature, increases nonlinearly with the decline of temperature. The variations of temperature at measuring points and freezing front with time are both symmertrical along the longitudinal of a soil sample under bidrectional freezing mode, and the development rate of freezing front is three times faster than that under unidirectional mode. It is practical for the freezing test with headspace under unidirectional mode in that the relationship between frost heave force and amount of frost heave could be got directly. These findings are useful for the design and construction of multi-coil piple freezing method and further study of frost heave model.

Key words: unidirectional and bidrectional freezing, amount of frost heave, frost heave force, freezing front, headspace