Artificial ground freezing (AGF), widely employed in subway tunnel construction, significantly alters the microstructure of surrounding soils through freeze-thaw processes. These changes become critical under subway operation, where traffic-induced dynamic loading can lead to progressive soil deformation. Understanding the dynamic behavior of freeze-thaw-affected soils is therefore essential for predicting and mitigating deformation risks. This study investigates the microstructural evolution of soil subjected to a single freeze-thaw cycle-representative of AGF practice-and subsequent dynamic loading. Dynamic triaxial tests were conducted under a fixed dynamic stress amplitude of 10 kPa and loading frequencies of 0.5 Hz, 1.5 Hz, and 2.5 Hz, simulating typical subway traffic conditions. Microstructural analyses were performed using mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Results show that the freeze-thaw cycle leads to a denser yet more disordered particle arrangement, with sharper and more angular particles, as reflected by increased probability entropy and reductions in surface porosity, form factor, and uniformity coefficient. Dynamic loading further causes particles to flatten and align in a more directional manner, accompanied by decreased surface porosity and form factor, and an increased uniformity coefficient. Pore structures become more uniform and less complex. Among various microstructural indicators, total intrusion volume from MIP displays a strong correlation with cumulative plastic strain, suggesting its potential as a micro-scale predictor of soil deformation. These findings enhance our understanding of the coupled effects of freeze-thaw and dynamic loading on soil behavior and offer valuable insights for improving the safety and durability of subway tunnel systems constructed using AGF.

来源平台：RESULTS IN ENGINEERING