Impact mechanical properties of frozen soil after experiencing freeze–thaw cycles: Experimental and numerical study

Abstract

When frozen soil serves as the foundation of engineering facilities in cold regions, it often suffers from the combined action of freeze–thaw cycles (FTC) and impact loading, which changes its stability and reliability. This study analyzed frozen soil by conducting FTC experiments with varying FTC numbers and impact loading experiments under varying strain rates. The experimental results revealed that frozen soil exhibited FTC and strain rate effects. The peak stress of frozen soil gradually weakened with a decrease in the strain rate and an increase in the FTC number. The expansion stress caused by the water–ice phase transition during an FTC was investigated, assuming that the expansion stress was comparable to the cyclic load, and the deterioration mechanism of frozen soil under the FTC action was discussed. An expression of FTC damage was derived using thermodynamic and continuous damage mechanical principles. A finite element model of frozen soil, derived from the cohesive zone model, was established by inserting cohesive elements into the common surfaces between solid soil elements. A traditional traction–separation (T–S) model for cohesive elements was improved by considering the influence of the strain rate using the overstress model. An elastic–plastic model was used to model the solid elements. The improved T–S model and elastic–plastic constitutive law were used to implement a numerical simulation via a user subroutine VUMAT integrated in ABAQUS/Explicit. When the FTC damage was considered, the microcrack evolution and impact mechanical behavior of frozen soil under impact loading after experiencing FTC action were observed. Having compared the numerical results with the experimental data, it is concluded that a good experimental–numerical correlation was obtained.