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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Why permafrost rocks become unstable: A rock-ice-mechanical model in time and space
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Why permafrost rocks become unstable: A rock-ice-mechanical model in time and space

机译：多年冻土岩石为何变得不稳定：时空的冰冰力学模型

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In this paper, we develop a mechanical model that relates the destabilization of thawing permafrost rock slopes to temperature-related effects on both, rock- and ice-mechanics; and laboratory testing of key assumptions is performed. Degrading permafrost is considered to be an important factor for rock-slope failures in alpine and arctic environments, but the mechanics are poorly understood. The destabilization is commonly attributed to changes in ice-mechanical properties while bedrock friction and fracture propagation have not been considered yet. However, fracture toughness, compressive and tensile strength decrease by up to 50% and more when intact water-saturated rock thaws. Based on literature and experiments, we develop a modified Mohr-Coulomb failure criterion for ice-filled rock fractures that incorporates fracturing of rock bridges, friction of rough fracture surfaces, ductile creep of ice and detachment mechanisms along rock-ice interfaces. Novel laboratory setups were developed to assess the temperature dependency of the friction of ice-free rock-rock interfaces and the shear detachment of rock-ice interfaces. In degrading permafrost, rock-mechanical properties may control early stages of destabilization and become more important for higher normal stress, i.e. higher magnitudes of rock-slope failure. Ice-mechanical properties outbalance the importance of rock-mechanical components after the deformation accelerates and are more relevant for smaller magnitudes. The model explains why all magnitudes of rock-slope failures can be prepared and triggered by permafrost degradation and is capable of conditioning long para-glacial response times. Here, we present a synoptic rock- and ice-mechanical model that explains the mechanical destabilization processes operating in warming permafrost rocks.
机译：在本文中，我们建立了一个力学模型，该模型将解冻的多年冻土岩石边坡的失稳与岩石和冰力学的温度相关影响联系起来。并对关键假设进行实验室测试。多年冻土的退化被认为是在高山和北极环境中岩质边坡破坏的重要因素，但对其机理知之甚少。不稳定通常归因于冰力学性质的变化，而尚未考虑基岩摩擦和裂缝扩展。但是，完整的水饱和岩石解冻剂的断裂韧性，抗压强度和抗拉强度最多降低50％，甚至更多。基于文献和实验，我们针对含冰岩石裂缝开发了修改后的Mohr-Coulomb破坏准则，该准则包括岩石桥梁的破裂，粗糙裂缝表面的摩擦，冰的延性蠕变以及沿冰冰界面的分离机制。开发了新型的实验室装置来评估无冰岩岩界面的摩擦和岩冰界面的剪切剥离的温度依赖性。在降解多年冻土时，岩石力学性质可以控制失稳的早期阶段，并且对于较高的法向应力（即较高的岩石边坡破坏程度）而言变得更加重要。变形加速后，冰力学特性使岩石力学组件的重要性失去了平衡，并且对于较小的震级更重要。该模型解释了为什么永久冻土退化可以触发所有级别的岩质边坡破坏，并且能够调节较长的冰川期响应时间。在这里，我们提出了一个天气岩石和冰层力学模型，解释了在变暖永冻土岩石中发生的机械失稳过程。

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