Closure of deep boreholes in ice sheets: a discussion
Closure of deep boreholes in ice sheets: a discussion
复制标题
DOI：
10.3189/172756407786857794
复制
发表时间：
2007
影响因子：
2.9
通讯作者：
P. Talalay;R. Hooke
中科院分区：
文献类型：
--
作者：
P. Talalay;R. Hooke
冰的变形速率和应力之间最常用的关系是幂律，通常称为格伦流动定律，其中A是冰的刚度参数，n是经验常数。A可以从简单的指数关系估算，其中A 0是与温度无关的常数; E，通常称为增强因子，取决于冰晶取向，杂质含量和其他因素; Q是蠕变的活化能; R是通用气体常数; T是绝对温度。室内试验的二次蠕变屈服值为A0 = 9.514MPa-3a-1。典型的井眼闭合实验则给出E = 0.16。这个低的值可能是由于这样的事实，即当变形到钻孔中时，冰受到的应力与c轴的优选取向不一致，c轴的优选取向在没有钻孔的应力配置下已经发展了很多年。东方号3G孔的闭合数据产生E = 0.7。这个较高的值可能反映了一个独特的应力环境，产生的织物，在某种程度上更好地定向钻孔关闭。
Abstract The most frequently used relation between ice deformation rate, έ, and stress, ፐ, is the power law, commonly called Glen’s flow law, έ = Aፐn , in which A is an ice stiffness parameter and n is an empirical constant. A can be estimated from the simple exponential relation where A 0 is a constant independent of temperature; E, commonly called the enhancement factor, depends on ice crystal orientation, impurity content and other factors; Q is the activation energy for creep; R is the universal gas constant; and T is the absolute temperature. Laboratory experiments yield values of A 0 = 9.514MPa–3a–1 for secondary creep. Typical borehole closure experiments then give E ≈ 0.16. This low value probably results from the fact that, when deforming into a borehole, ice is subject to stresses that are inconsistent with the preferred orientation of c axes that has developed over many years under a stress configuration with no borehole present. Closure data from Vostok hole 3G yield E ≈ 0.7. This higher value may reflect a unique stress environment yielding fabrics that are somewhat better oriented for borehole closure.