Water content variations during unsaturated feet-scale soil freezing and thawing

Abstract

In this study, we experimentally investigated the variations in water content during feet-scale soil freezing and thawing processes, and two particular water content variations were observed in the freezing and thawing processes. In the freezing process, experimental results revealed that the water content increased initially with an abrupt drop at temperatures close to the bulk water freezing point (T0 = 0 °C). In the thawing process, two water content drops were observed at the initial and final stages of soil melting. In our opinion, the unusual increases and decreases in water contents are the results of state change between freezing and evaporation of pore water in top soil. Water content variations were calculated based on the initial water potential distribution by using two fitting functions, they agreed well with the unusual increases and decreases in the water contents, indicating that the unusual increases and decreases in the water content somehow related to the evaporation of pore water in top soil.