In the process of unidirectional freezing

the generation and development of segregating ice is an important factor affecting the structural characteristics of frozen and thawed soil. Three unidirectional freezing boundary conditions were selected

i.e.

cooling rate (from 0.5 ℃/s to 0.005 ℃/s)

cold temperature (from –30 ℃ to –70 ℃)

and water replenishment (no water replenishment

constant pressure water replenishment) to explore their influence on the development of segregating ice. To facilitate the measurement of segregating ice

an independent meso-measurement system has been developed using optical microscope digital photography. This system enables in-situ and non-contact measurement of segregating ice cracks. The experimental results demonstrate the following findings: (i) The distribution of segregating ice is not only influenced by temperature gradients and warm end replenishment conditions

but also by the cooling rate at the cold end of the unidirectional freezing process. (ii) The width of the segregating ice in the frozen area is more significantly affected by the movement rate of the frozen front than by the temperature gradient. (iii) During the freezing process

the width of the frozen ice exhibits an exponential relationship with the movement rate of the 0 ℃ line. Based on this characteristic

an empirical formula is proposed to predict the crack width of segregating ice in the frozen zone. This formula can be used as a reference for evaluating unilateral frost heave failure in practical engineering construction

particularly under conditions of varying cooling rates.