Abstract: Water vapor supply can induce frost heave of sand filler. Based on the self-developed moisture migration and frost heaving tester, the variations of sand moisture content, temperature and frost heave with freezing time under gaseous water recharge were studied. The change characteristics of sand microstructure during freezing were examined by stereomicroscope. By combining with the grey correlation theory, the correlation between the macroscopic index, i.e., frost heave and the microscopic parameters was analyzed. Notable frost heaving was observed under water vapor supply, and the frost heave reached 3.45 mm after 7 days of freezing. After sandy soil frost heaving, the proportion of large pore area increased and the proportions of small and medium micropore area decreased, and the change trend of pore number proportion was opposite to that of area proportion, while pore abundance value changed little, pore orientation angle distribution in each interval tended to be more uniform, the probability entropy of pore orientation present an overall upward trend of oscillation, and the pore fractal dimension showed a trend of decrease. In addition, the grey correlation theory is used to establish the correlation between the frost heave and the average pore size and other microscopic parameters, which provides an insight into the microscopic mechanism of sand frost heaving under water vapor supply.

Key words: sandy soil, water vapor supply, frost heave, microstructure characteristics, microstructure parameter