Artificial Ground Freezing—On the Soil Deformations during Freeze–Thaw Cycles

Abstract

Artificial ground freezing (AGF) has emerged as a prominent treatment method due to its ability to mechanically strengthen the soil while reducing its permeability. However, its implementation has raised concerns about its impact, particularly with respect to frost heave and subsequent thaw-induced displacements. These soil movements can cause subsidence and pose a significant threat to the integrity of surface structures. Overburden pressure plays a crucial role in AGF and determines the amount of heave generated. This paper presents an analysis of the existing literature about soil freezing and thawing. The aim is to offer an understanding of these processes, specifically with regard to their application in AGF. This paper explains the behavior of soil during freezing, with particular emphasis on the influence of overburden pressure. It also investigates frozen soils’ thawing and freeze–thaw (FT) cycles’ long-term effects on soil properties. AGF offers improved soil strength and reduced water permeability, enhancing construction project stability. However, the interplay between the temperature, soil composition, and initial ground conditions during freezing is complex. This thermo-hydro-chemo-mechanical process strengthens the soil and reduces its permeability, but it can also induce frost heave due to water expansion and ice lens formation. Overburden pressure from the overlying soil limits ice lens growth. FT cycles significantly impact soil properties. In fine-grained soils, FT cycles can lead to over-consolidation, while rapid thawing can generate high pore pressures and compromise stability. Importantly, FT acts as a weathering mechanism, influencing soil properties at both the microscopic and macroscopic scales. These cycles can loosen over-consolidated soil, densify normally consolidated soil, and increase overall hydraulic conductivity due to structural changes. They can also weaken the soil’s structure and deteriorate its mechanical performance.

Keywords

• artificial ground freezing
• freeze–thaw cycle
• overburden pressure
• frost heave
• thaw–settlement