Water ice Ih exhibits brittle behavior when rapidly loaded. Under tension, it fails via crack nucleation and propagation. Compressive failure is more complicated. Under low confinement, cracks slide and interact to form a frictional (Coulombic) fault. Under high confinement, frictional sliding is suppressed and adiabatic heating through crystallographic slip leads to the formation of a plastic fault. The coefficient of static friction increases with time under load, owing to creep of asperities in contact. The coefficient of kinetic (dynamic) friction, set by the ratio of asperity shear strength to hardness, increases with velocity at lower speeds and decreases at higher speeds as contacts melt through frictional heating. Microcracks, upon reaching a critical number density (which near the ductile-to-brittle transition is nearly constant above a certain strain rate), form a pathway for percolation. Additional work is needed on the effects of porosity and crack healing. ▪ An understanding of brittle failure is essential to better predict the integrity of the Arctic and Antarctic sea ice covers and the tectonic evolution of the icy crusts of Enceladus, Europa, and other extraterrestrial satellites. ▪ Fundamental to the brittle failure of ice is the initiation and propagation of microcracks, frictional sliding across crack faces, and localization of strain through both crack interaction and adiabatic heating.

中文翻译：

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冰的裂缝、摩擦和渗透性


水冰 Ih 在快速加载时表现出脆性行为。在张力下，它通过裂纹成核和扩展失效。压缩破坏则更为复杂。在低约束下，裂纹滑动并相互作用形成摩擦（库仑）断层。在高约束下，摩擦滑动受到抑制，通过晶体滑移产生的绝热加热导致塑性断层的形成。由于接触中的凹凸不平的蠕变，静摩擦系数在负载下随时间增加。动（动态）摩擦系数由粗糙剪切强度与硬度的比值设置，在较低速度下随速度增加，在较高速度下随着接触通过摩擦加热熔化而降低。微裂纹在达到临界数密度（在韧性到脆性转变附近几乎恒定，高于一定应变速率）时，形成渗流途径。需要对孔隙率和裂纹愈合的影响进行额外的研究。▪ 了解脆性破坏对于更好地预测北极和南极海冰覆盖的完整性以及土卫二、木卫二和其他地外卫星冰壳的构造演变至关重要。▪ 冰脆性破坏的基础是微裂纹的产生和扩展、裂纹表面的摩擦滑动以及通过裂纹相互作用和绝热加热实现应变的局部化。