Numerical investigation of the path-dependent frost heave process in frozen rock under different freezing conditions

Frost heave in water-bearing rock masses poses significant threats to geotechnical engineering. This paper developed a novel three-dimensional (3D) frost model, based on the combined finite-discrete element method (FDEM), to investigate the frost heave process in rock masses where thermal transfer, water migration, water-ice phase transition (ice growth) and ice-rock interaction are explicitly simulated. The proposed model is first validated against existing experimental and analytical solutions, and further applied to investigate path-dependent frost heave behavior under various freezing conditions. Results show that freezing direction plays a vital role in the dynamic ice growth and ice-rock interaction, thus affecting the frost heave behavior. In the top-down freezing regime, ice plugs form first at the crack's top surface, sealing the crack and preventing water migration, which can amplify ice pressure. Parametric studies, including rock Young's modulus, ice-rock friction, and rock hydraulic conductivity, further reveal that the temporal aspects of ice development and rock mechanical response strongly affect ice-rock interaction and hence the frost heave mechanism. Furthermore, some typical phenomena (e.g. water/ice extrusion and frost cracking) can also be well captured in this model. This novel numerical framework sheds new light on frost heave behavior and enriches our understanding of frost heave mechanisms and ice-rock interaction processes within cold environment engineering projects.