Influence of freeze-thaw cycles in the presence of a supplementary water supply on mechanical properties of compacted soil

In seasonal frozen regions where the groundwater is relatively shallow, the upward migration of groundwater during the freezing process will change the moisture content of the subgrade soil after freeze-thaw (F-T) cycles. This study attempted to investigate the deterioration effect of F-T cycles in combination with available groundwater migration on the mechanical properties of compacted clayey soil. For this purpose, the compacted clay specimens were frozen and thawed from the top to bottom and external water was supplied from the bottom of the samples. Specimens with different initial states (i.e. different initial dry densities and initial moisture contents) were subjected to different number of F-T cycles. The changes in moisture content and frost heave after the F-T cycles were measured. The failure strength and elastic modulus of the soil then were determined using unconsolidated and undrained triaxial compression tests. The results of the study demonstrated that water replenishment of the soil during the freezing process had considerable influence on the mechanical properties of soil, and the availability of a supplementary water supply could accelerate the development of stable state in the failure strength and the elastic modulus of soil. Moreover, the reduction rates of failure strength and elastic modulus reached 85% and 92% after 7 F-T cycles, respectively. The degradation effect of the F-T cycles on the mechanical property of soil can be reduced by enhancing the dry density or by moderately raising the moisture content of soil. Finally, the fitted models describing the combining effects of F-T cycles, initial dry density, initial moisture content and confining pressure on the failure strength and elastic modulus of soil were developed and verified by the experimental data to be rational and reliable.