Effect of freeze-thaw on freezing point and thermal conductivity of loess

Evaluation of freeze-thaw induced instability of loess slopes required a rational estimation of thermal indexes of loess. Freezing point and thermal conductivity of loess after freeze-thaw were determined by laboratory tests, and correlations with mesoscopic structure were discussed by SEM tests. Freezing point of loess grows nonlinearly with water content but rarely correlated with dry density, while it varies significantly within initial five freeze-thaw cycles, beyond which little effect was noted. Thermal conductivity increases positively with water content or at higher dry densities. Besides, bi-directional changes with dry density were noticed. SEM images prove that large aggregates decrease after freeze-thaw with weak bonding between particles, leading to a loosened soil structure, which corresponds to the variation of thermal indexes. Empirical models for the two indexes were proposed based on data fitting.