Anti-seepage mechanism of frozen curtains in high-permeability sandy soils: An experimental study

Seepage in underground engineering is a prevalent challenge within construction projects, where conventional anti-seepage technologies are often constrained by high costs and limited environmental adaptability. As an economical and environmentally friendly alternative, the artificial ground freezing method demonstrates significant advantages in addressing complex engineering scenarios, such as those involving highly permeable sandy soils. However, a systematic investigation into its anti-seepage mechanism remains insufficient. Therefore, this study employs laboratory experiments to quantitatively investigate the influence of multiple factors, including pressure, temperature, and time, on the evolutionary patterns of porosity and permeability within a frozen curtain. The results indicate a significant equivalent relationship between freezing temperature and time; for instance, complete pore elimination is achieved in just 20 min at −10 °C, whereas it requires over 60 min at 0 °C. The permeability characteristics of the frozen curtain are governed by the synergistic effects of temperature, pressure differential, and moisture content. Under a cyclic temperature of 0 °C, the permeability can be maintained at an extremely low level of 0.0015 g/s even after 240 min. Ambient temperature is the dominant factor in maintaining the stability of the frozen curtain; when the temperature exceeds 10 °C, the thawing process accelerates significantly, yet the permeability after 240 min remains lower than that of the completely unfrozen state. Furthermore, the influence of moisture content on freezing effectiveness is constrained by temperature conditions: when the temperature is below −10 °C, zero porosity can be achieved within 10 min, regardless of the moisture content. These findings provide a crucial theoretical basis for optimizing the design and construction of ground freezing projects in highly permeable sandy soil strata.