Effects of cyclic freezing and thawing on mechanical properties of Qinghai-Tibet clay

A fine-grained clay was compacted in the laboratory and was thereafter exposed to a maximum of 21 closed-system freezing and thawing cycles. The sample height, water content, stress-strain behavior, failure strength, elastic modulus, cohesion and friction angle were measured in initial unfrozen soil as well as in subsequent thawed soil. The results show that the physical-mechanical characteristic of investigated soils changed after it was subjected to freeze-thaw cycles. The height of sample increased and water content decreased before the sample exposed to 7-10th cycle of freeze-thaw, but both the height and water content remained constant after the 7th freeze-thaw. The shape of the stress-strain behavior curves were not affected by the freeze-thaw process, but the resilient modulus and the failure strength were heavily influenced by the number of freeze-thaw cycles. The minimal values for both the resilient modulus and the failure strength were frequently achieved after the specimen was exposed to about 3-7 freeze-thaw cycles, therefore, the resilient modulus and the failure strength of soils experienced seven freeze-thaw cycles could be applied to the process of cold region engineering design. For the soil investigated, the cohesion decreased with the increasing number of freeze-thaw cycles, and the friction angle exhibit an increasing trend. (c) 2006 Elsevier B.V All rights reserved.