Effect of shear rupture on aggregate scale formation in sea ice
Effect of shear rupture on aggregate scale formation in sea ice
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DOI：
10.1029/2009jc006043
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发表时间：
2010-10-02
影响因子：
3.6
通讯作者：
Hopkins, Mark A.
中科院分区：
文献类型：
--
作者：
Wilchinsky, Alexander V.;Feltham, Daniel L.;Hopkins, Mark A.
采用离散元模型研究了辐合风应力作用下海冰的剪切破裂。该模型包括连接在风应力作用下移动的浮体的粘弹性节理的压缩破裂、拉伸破裂和剪切破裂。所采用的剪切破坏遵循库仑准则。浮冰群是一个400公里长的正方形区域，由4公里大小的浮冰组成。在抗拉强度小于抗压强度10倍的标准情况下，在单轴压缩下，破坏形式主要为剪切破坏，最可能的情况对应于破坏功最小的情况。描述形成的聚集体的裂纹方向是双峰的，其峰围绕由翼裂纹理论给出的确定菱形块的角度。随着风应力梯度的增大，冰块（浮体）粒径减小，因为弹性应变能增长更快，导致裂纹扩展速度加快。随着抗拉强度的增加，剪切破坏变得越来越难实现，压缩破坏变得同样重要，导致垂直于压缩方向的块体伸长和块体变大。在标准情况下，随着风应力约束比的增大，约束比在0.2 ~ 0.4范围内发生破坏模式变化，对应于解析临界约束比为0.32。低于这个值，裂缝是双峰的，描绘出钻石形状的集合体，而高于这个值，破坏就变成各向同性的，由不规则的碎块形状引起的小尺度应力异常决定。
A discrete element model is used to study shear rupture of sea ice under convergent wind stresses. The model includes compressive, tensile, and shear rupture of viscous elastic joints connecting floes that move under the action of the wind stresses. The adopted shear rupture is governed by Coulomb's criterion. The ice pack is a 400 km long square domain consisting of 4 km size floes. In the standard case with tensile strength 10 times smaller than the compressive strength, under uniaxial compression the failure regime is mainly shear rupture with the most probable scenario corresponding to that with the minimum failure work. The orientation of cracks delineating formed aggregates is bimodal with the peaks around the angles given by the wing crack theory determining diamond-shaped blocks. The ice block (floe aggregate) size decreases as the wind stress gradient increases since the elastic strain energy grows faster leading to a higher speed of crack propagation. As the tensile strength grows, shear rupture becomes harder to attain and compressive failure becomes equally important leading to elongation of blocks perpendicular to the compression direction and the blocks grow larger. In the standard case, as the wind stress confinement ratio increases the failure mode changes at a confinement ratio within 0.2-0.4, which corresponds to the analytical critical confinement ratio of 0.32. Below this value, the cracks are bimodal delineating diamond shape aggregates, while above this value failure becomes isotropic and is determined by small-scale stress anomalies due to irregularities in floe shape.