ARTIFICIAL GROUND FREEZING: ROLE OF OVERBURDEN PRESSURE IN THE THERMO-HYDRO-MECHANICAL BEHAVIOR OF SILTY SAND DURING A FREEZE-THAW CYCLE

Artificial Ground Freezing (AGF) enhances soil strength and reduces permeability, but managing frost heave and thaw-induced deformations remains a major challenge. In deep excavations, overburden pressure plays a critical yet complex role in these processes. To investigate this, freeze-thaw (FT) tests were performed on silty sandy soil under applied stresses ranging from 10 to 4000 kPa using a temperature-controlled (TC) oedometer. Results show a strong inverse relationship between stress and frost heave; higher stress limits ice lens formation and associated deformations. Across all stress levels, the FT cycle induces soil densification, resulting in net volume reduction after thawing. However, the post-thaw mechanical behavior depends on the stress applied during freezing. Under low stress (10–30 kPa), FT increases compressibility, weakening the soil despite densification. In contrast, higher stresses reduce compressibility and enhance stiffness, effectively mitigating FT-related damage. Notably, heave is eliminated under 4000 kPa, suggesting the existence of a threshold stress beyond which FT deformations are fully suppressed.