Influence of freeze-thaw cycles on mechanical properties of a silty sand

Freeze-thaw cycling is a very common phenomenon in seasonally frozen soil areas and it will affect the mechanical properties of soils which should be taken into account for geotechnical engineering. To study the variation of mechanical properties of seasonally frozen soils, fine-grained silty sand was compacted in the lab and was then exposed to a maximum of 12 closed-system freeze-thaw cycles. The stress-strain curve, failure strength, elastic modulus, cohesion and angle of internal friction were measured for samples before and after the freeze-thaw cycles. The mechanical properties were considerably affected by the number of freeze-thaw cycles, whereas the influence of cooling temperature was not obvious. The highest decrease rate of elastic modulus was about 26%-45% and for failure strength it reached at 32%-45% compared to the unfrozen soil which did not experience the freeze thaw cycles. The cohesion decreased after the first few freeze-thaw cycles and then kept nearly stable after about 9-12 cycles while the internal friction angle decreased at first and then increased during the freeze-thaw cycles, reaching the minimum values at about the 7 cycles. The method of significance was used to analyze the influence of different factors. Results showed that the number of freeze-thaw cycles had significant influence on the mechanical properties and the cooling temperature had less influence. The normalized stress-strain relationship considering the influence of freeze-thaw cycling as well as confining pressure was established and can predict the stress-strain relation well compared with the experimental data. (C) 2016 Elsevier B.V. All rights reserved.