Abstract
Abstract. A temperature- and stress-dependent failure criterion for ice-filled rock (limestone) joints was proposed in 2018 as an essential tool to assess and model the stability of degrading permafrost rock slopes. To test the applicability to other rock types, we conducted laboratory tests with mica schist and gneiss, which provide the maximum expected deviation of lithological effects on the shear strength due to strong negative surface charges affecting the rock–ice interface. Retesting 120 samples at temperatures from −10 to −0.5 ∘C and normal stress of 100 to 400 kPa, we show that even for controversial rocks the failure criterion stays unaltered, suggesting that the failure criterion is transferable to mostly all rock types.
Highlights
Climate-related changes in the thermal conditions in steep bedrock permafrost can lead to rock slope destabilization or failure (e.g. Gruber and Haeberli, 2007), potentially triggering large-scale hazards via process chains (Huggel et al, 2012)
As Fischer et al (2012) demonstrated that gneiss and schist are among the most relevant rock types involved in rock slope failures within the Alpine mountain permafrost belt, this study aims at testing the applicability of the failure criterion for those rock types
This study demonstrates that the failure criterion by Mamot et al (2018) is surprisingly resilient as it can be applied to (i) different failure types including the fracture in ice and along the rock–ice contact, (ii) a wide range of temperatures relevant for bedrock permafrost (−0.5 to −8 ◦C), (iii) a wide range of relevant stress conditions (100–400 kPa) and (iv) mostly all rock types relevant for permafrost rock slope failures in the Alps, as the metamorphic mica-rich rocks tested in this study represent the expected maximum deviation of potential lithological effects on the shear strength of ice-filled rock joints
Summary
Climate-related changes in the thermal conditions in steep bedrock permafrost can lead to rock slope destabilization or failure (e.g. Gruber and Haeberli, 2007), potentially triggering large-scale hazards via process chains (Huggel et al, 2012). A number of failures in bedrock permafrost have exposed residual ice at their shear and detachment planes (Keuschnig et al, 2015; Phillips et al, 2017; Ravanel et al, 2017; Weber et al, 2018; Walter et al, 2020). These observations indicate the occurrence of ice-filled rock discontinuities and their importance as a controlling factor for the stability of degrading permafrost rock slopes. The unfrozen shear strength is 400–1000 kPa lower when compared with the one of ice-filled joints at temperatures between −2 and −10 ◦C
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