Pore water pressure changes of supercooling and ice nucleation stages during freezing point testing

Investigation of the pore water pressure during soil freezing is essential for exploring frost heave mechanisms such as water migration and the initiation of ice lenses. The pore water pressures of fine-grained silty clay were measured during freezing point testing under closed-system conditions. Two soil samples, with degrees of saturation of 63⋅03 and 69⋅60%, were tested. Based on the experimental results, soil freezing during freezing point testing was divided into three stages – supercooling, free water freezing and bound water freezing. Supercooling and ice nucleation stages were definitely observed during freezing point testing. The pore water pressure remained almost constant during the supercooling stage but increased slightly during ice nucleation. The pore water pressure change was related to the freezing process of pore water in different states.