Impact of freeze-thaw on the physical properties and compressibility of saturated clay

摘要

Artificial ground freezing (AGF) has been widely applied in underground construction and ground deformation, particularly, thaw settlement, induced by AGF are of great concerns in soft soils. This paper describes an apparatus for simulating unidirectional freezing with or without water supply and presents the variations in physical characteristics including moisture content, void ratio, and dry density of saturated clay due to freeze-thaw (F-T) under different overburden pressure and water supply conditions. Further, consolidation tests were carried out to study the change in compressibility parameter along the specimen height due to F.T. It was found that the soil index properties and consolidation parameters including the pre-consolidation pressure and compression and swell indices change significantly due to F-T and the changes are not uniform in the unfrozen and frozen zones. For F-T under an overburden pressure with water supply, the pre-consolidation pressure increases in both the unfrozen and frozen zones. It was also found that the increase in the pre-consolidation pressure is almost proportional to the overburden pressure in the unfrozen zone but is largely insensitive to the overburden pressure in the frozen zone. Furthermore. This study demonstrates that F-T triggers a re-consolidation in clays that is significant for cases where large overburden pressure is present during ground freezing and further study is needed to understand the mechanisms responsible for these changes, and how sample preparation methods, freezing methods and temperatures, and soil index properties may affect soil compressibility, and how to estimate the settlement post F-T.