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 labora-tory 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 sur-face 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.

Automated summary

In this study, a novel in-flight freeze-thaw system was used to investigate the thermal, hydraulic, and mechanical response of a typical unsaturated slope under seven freeze-thaw cycles in the centrifuge. The test results showed that the suction at the freezing front can be up to about 1 MPa, and subsequent thawing reduces the suction to 9 kPa, about 60% lower than the initial unfrozen state. The repeated freeze-thaw action generates significant fractures at the soil surface and deep cracks due to tensile rupture.