Effects of Freeze–Thaw Cycles on Volume Change Behavior and Mechanical Properties of Expansive Clay with Different Degrees of Compaction

Abstract

Freeze–thaw (F-T) cycles are one of the main deterioration factors for the performance of expansive clay in seasonally frozen soil regions. This study designed a unidirectional environmental boundary loading device for F-T cycle tests. Laboratory tests were conducted to quantitatively evaluate the effects of the F-T cycle on volume change behavior and mechanical properties of expansive clay with different degrees of compaction below the canal in Xinjiang. The SEM image processing was performed with the Image-Pro Plus image processing software to get pore parameters. The results showed that during the F-T cycle, the volume change of the sample gradually changes from contraction to expansion as the degree of compaction increases. As the degree of compaction increases, the hardening characteristics of the expansive clay are weakened, and the F-T cycle promotes the softening of the stress–strain relationship. The first F-T cycle resulted in a significant decrease of failure strength, and the failure strength of different compaction degrees decreased by 56.07%–67.54% after seven cycles. The failure strain and resilient modulus of the samples are attenuated to varying degrees after F-T cycles. The correlation rate between the porosity and the attenuation rate of the failure strength is 0.719–0.882, the corresponding weight reaches 0.419–0.445, and there is an excellent linear relationship between them. The research offers some important insights into the construction and maintenance of expansive clay engineering such as the Xinjiang Canal.