Abstract: The freezing-thawing experiments were performed to investigate the effect of pre-freezing moisture content and dry density on the compression and water migration in Qinghai-Tibet silty clay under double-direction freezing and one-direction thawing. The results show that (1) under large thermal gradients, the compressibility of the soil decreases at low initial densities and increases at high initial densities after freeze-thaw cycles, whereas under small thermal gradients, the soil compressibility constantly decreases; (2) As the pre-freezing moisture content increases, the soil compressibility under larger thermal gradients increases and approaches to a stable value, whereas it remains practically unchanged under small thermal gradients; (3) As the thermal gradient increases, all the compressibility coefficients of melted soils at different densities decrease first, and then increase, and the compressibility coefficients of melted soils under different pre-freezing water contents increase; (4) The water contents in the frozen specimen first increase, then decrease and finally increase from the top to the bottom. As the thermal gradient descends, the water content in the middle part of the specimen increases first and then decreases.

Key words: freeze-thaw cycle, double direction freezing-one direction thawing, compression deformation, water migration, melted soil compression coefficient