Shear strength-temperature-moisture content relationship of warm frozen ground for thaw slump stability analysis

Permafrost covers nearly 50 % of Canada, which is where intense climate warming is occurring four times faster than the global average. These factors have led to a significant increase in geohazards, including landslides, thawing glaciers, mass wasting, and instability in ice-rich soils. Retrogressive thaw slumps have increased by 60 % in recent decades raising concerns for linear infrastructure, built environment, community, and the environment. Previous research includes both site-specific and remote studies seeking to understand controlling factors of thaw slumps and triggering mechanisms that lead to a range of potential outcomes from significant retrogression, slumping, or self-stabilization. Recently physical modelling in a geotechnical centrifuge has shown that the thaw slump outcome (retrogression through self-stabilization) occurs at temperatures near 0 °C and that ice content plays a significant role. Shear failures observed during physical models give motivation to complete limit equilibrium analysis, however, the shear strength relationship is unknown and difficult to accurately measure in warm frozen ground (between −1 and 0 °C). In this paper, the shear strength-temperature-moisture content relationship of warm frozen ground is reported and used in stability analysis of shear failure thaw slumps. Results showed that shear strength significantly decreases between −1 and 0 °C and then remains constant at positive temperatures. Shear strength is very sensitive to changes in both temperature below zero and moisture content at positive and negative temperatures. Results were implemented in slope stability analyses to illustrate the high sensitivity of factor of safety to temperature and ice/moisture content in thawing fine-grained materials. • Thaw slumps are occurring at increased frequency due to climate warming. • Physical modelling of thaw slumps allows for direct observation of failure and triggering mechanisms. • Measured coupled shear strength-temperature-moisture content relationship for warm frozen ground. • Shear strength implemented in illustrative thaw slump stability analyses.