Investigation of slope deterioration mechanism under freeze-thaw cycles: centrifuge modelling

Although deterioration of soil due to freeze-thaw cycles has been investigated based on element tests and small-scale laboratory model tests, there still lacks fundamental understanding of slope response under cyclic freeze-thaw action. In this study, a novel in-flight freeze-thaw system was developed to investigate the thermal, hydraulic and mechanical response of a typical unsaturated slope under seven freeze-thaw cycles in the centrifuge. Temperature, suction and deformation were measured during the test. The test results show that the suction at the freezing front can be up to about 1 MPa. The comparison between measured and theoretically predicted suction elucidates that using the temperature-dependent Clausius-Clapeyron equation is inadequate to model suction evolution precisely when considering water migration. The subsequent thawing reduces the suction to 9 kPa, which is about 60% lower than during the initial unfrozen state. The suction destruction softens the surface soil layer, leading to downslope movement during thawing. During the seasonal downward ratcheting movement, the lower elevation of the slope can flatten from 59? to 50?. The repeated freeze-thaw action generates significant fractures at the soil surface while deep cracks can form due to tensile rupture. Freeze-thaw-induced seasonal variation of suction softens the post-thawed slope, leading to accumulated plastic deformation and shallow slope failure.