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Calculating cumulative strain in .NET Printing Code 39 in .NET Calculating cumulative strain




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Calculating cumulative strain use .net vs 2010 3 of 9 writer toprint barcode 3/9 for .net International Standard Serial Numbers (a) g (b) g Depth, m q q j Figure 13.6. Calculat .

net framework 39 barcode ed variation of oc , yi c , and c with depth at locations of Barnes Ice Cap boreholes (a) T020 and (b) T081. Locations of boreholes are shown in Figure 13.5.

(From Hooke and Hudleston, 1980, Figures 8a and 9a. Reproduced with permission of the International Glaciological Society.).

orientations of the a xes of maximum cumulative extension (X-axes: Figure 13.5b). Noteworthy in this gure is the fact that these axes are nearly parallel to the bed throughout most of the glacier.

The increased upglacier dip at the surface near and downglacier from borehole T061 is a consequence of the increase in the ratio of simple shear to pure shear as the equilibrium line is approached. As just noted, in simple shear the axis of maximum elongation dips 45 initially; with increasing deformation it is gradually rotated toward parallelism with the plane of the shear. The cumulative strain magnitude, oc , is shown in Figure 13.

5c. These numbers do not appear signi cant until one realizes that oc is proportional to the natural logarithm of the axial ratio of the strain ellipse. Thus, oc = 8, found in the most basal ice, corresponds to an elongation of 18 000:1.

A 1 m cube would be stretched into a 1-m wide ribbon 134 m long and 7.5 mm thick! Figure 13.6 shows the variation of oc , c , and c with depth in boreholes T020 and T081 (Figure 13.

5a). Because the dominant strain pattern at T020, particularly in the upper part of the glacier, is nearly pure shear with vertical compression and longitudinal extension, the axis of maximum cumulative extension is nearly horizontal. Thus, c remains close to 0.

On the other hand, c is 0 at the surface and initially increases. Finite strain and the origin of foliation gradually with depth as u/ z increases. However, with increasing depth in the glacier, the ice arriving at T020 has passed through a larger and larger region dominated by pure shear (Figure 13.4).

Thus, c reaches a maximum ( 12 ) at a depth of 240 m and then decreases at greater depth. The pattern at the site of borehole T081 is different in several respects. Because this hole is in the upper part of the ablation area, ice at the surface accumulated some strain as it moved from higher in the glacier.

Thus, oc > 0 at the surface. With increasing depth, the ice has traveled a greater distance and accumulated more strain so oc increases to about 7, representing an axial ratio of over 5000. Because ice near the surface has experienced a modest amount of mixed simple and pure shear (Figure 13.

4), c 10 and c 25 here. With increasing depth, c rst increases, reaching a maximum at a depth of 120 m and then decreases, re ecting the early history of pure shear that this deeper ice experienced. To further quantify the in uence of the early history of pure shear, Hudleston calculated c for a particle of ice that experienced a total strain, oc , of 3.

75 entirely by simple shear (Hooke and Hudleston, 1980). In this case, c is 80 and increases toward 90 as oc increases further. For comparison, in holes T020 and T081 the actual rotations at this strain magnitude are 9 and 57 , respectively.

Let us now use our understanding of cumulative strain to study the origin of foliation.. Components of foliation The pronounced banded character of glaciers (see, for example, Figures 5.18 and 8.8) has led to considerable confusion.

Banding is most prominent in the ablation area once the winter snow has melted. However, banding may also be seen in crevasse walls in the accumulation area, although it has a very different appearance there and most people would, correctly, refer to it as annual layering or sedimentary strati cation. The banding is normally subparallel to the nearest bounding surface, be it the bed, the surface, or the valley walls.

However, in the lower part of the ablation area it typically dips gently to steeply upglacier (Figure 13.7b). The banding is penetrative; that is, the bands are cross sections of layers in the ice.

On close inspection, one nds that the banded appearance most commonly results from variations in bubble or dirt content. The latter, coupled with the suggestive upglacier dip of the bands near the margin, has given rise to the mistaken impression that the banding is a re ection of shear planes in the ice along which debris was (somehow) carried to the.
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