Freeze–thaw impacts on the mechanical behavior of silty clay: Insights from experimental and DEM investigation

Abstract

Seasonally frozen soil areas experience freeze–thaw cycles (FTCs), which affect the soil's mechanical properties and should be considered during geotechnical engineering applications. Therefore, understanding the micro-mechanism of soil's macro-mechanical characteristics exposed to the FTCs is necessary. This study explored the impact of FTCs on the macro–micro properties of silty clay by performing F-T tests, triaxial compression tests, and the corresponding Distinct Element Method (DEM) simulations. The effect of FTCs on the macroscopic shear properties of silty clay in Sichuan Province, including stress–strain behavior, peak deviatoric stress, cohesion, and internal friction angle, was investigated utilizing laboratory triaxial compression tests. In addition, a novel approach based on DEM, which considers the expansion–contraction influence of ice particles on the pores and the impact of FTCs on the structure of granular soils, was developed to simulate the fabric evolution of granular soils after FTCs. According to the results, macroscopically, failure strength, internal friction angle, and cohesion were in a decrement trend as FTCs increased. On the microscopic scale, with the increase of the FTCs, the degree of soil anisotropy decreased, and the contact and force fabric anisotropy coefficients decreased, which contributed to the decrease in macroscopic shear strength. In addition, a linear and unique relationship was detected between the macroscopic stress ratio q/p of the granular system and the microstructural stress ratio of the strong contact network \({\Phi }_{d}^{s}/{\Phi }_{m}^{s}\), independent of the number of FTCs. Increased FTCs caused a rearrangement of weakly contacted networks, resulting in macroscopically different mechanical behavior.