A thermomechanical model for frost heave and subglacial frozen fringe
A thermomechanical model for frost heave and subglacial frozen fringe
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DOI：
10.1017/jfm.2023.366
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发表时间：
2021-09
影响因子：
3.7
通讯作者：
C. Meyer;C. Schoof;A. Rempel
中科院分区：
文献类型：
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作者：
C. Meyer;C. Schoof;A. Rempel
冰渗透沉积物或冰冻边缘是造成冻胀、冰透镜和冰川下数米富含碎片的冰等现象的原因。了解冰冻边缘很重要，因为冻胀会破坏高纬度地区的基础设施，而冰川底部的沉积物冻结可以调节冰下摩擦，影响全球海平面上升的速度。在这里，我们描述了冰饱和沉积物中液态水流动和冻结的热力学，重点是与冰下环境相关的条件。控制冻结边缘厚度的力平衡取决于上覆物质的重量、冰和沉积物之间通过液体预熔膜的热分子力以及达西流所需的水压。我们将这种力学模型与在固定计算网格上保存相变界面能量的焓法相结合。力平衡和焓模型共同决定了冻结条纹厚度的演变，我们的模拟预测了冻胀率和冰透镜间距。我们的模型考虑了冰-沉积物接触处的预融化、孔隙空间的部分冰饱和、水通过边缘的流动、冰-水-沉积物界面的热力学和垂直力平衡。我们明确地解释了冰透镜的形成，即在粒子间力消失的深度切割条纹的纯冰区域。我们的模型结果使我们能够预测冻结边缘的厚度以及地表和冰下沉积物中冰透镜的间距。
Abstract Ice-infiltrated sediment, or frozen fringe, is responsible for phenomena such as frost heave, ice lenses and metres of debris-rich ice under glaciers. Understanding frozen fringes is important as frost heave is responsible for damaging infrastructure at high latitudes and sediment freeze-on at the base of glaciers can modulate subglacial friction, influencing the rate of global sea level rise. Here we describe the thermomechanics of liquid water flow and freezing in ice-saturated sediments, focusing on the conditions relevant for subglacial environments. The force balance that governs the frozen fringe thickness depends on the weight of the overlying material, the thermomolecular force between ice and sediments across liquid premelted films and the water pressure required by Darcy flow. We combine this mechanical model with an enthalpy method that conserves energy across phase change interfaces on a fixed computational grid. The force balance and enthalpy model together determine the evolution of the frozen fringe thickness and our simulations predict frost heave rates and ice lens spacing. Our model accounts for premelting at ice–sediment contacts, partial ice saturation of the pore space, water flow through the fringe, the thermodynamics of the ice–water–sediment interface and vertical force balance. We explicitly account for the formation of ice lenses, regions of pure ice that cleave the fringe at the depth where the interparticle force vanishes. Our model results allow us to predict the thickness of a frozen fringe and the spacing of ice lenses in subaerial and subglacial sediments.