A ring-shear device for the study of till deformation: Tests on tills with contrasting clay contents
A ring-shear device for the study of till deformation: Tests on tills with contrasting clay contents
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DOI：
10.1016/s0277-3791(97)00036-x
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发表时间：
1997
影响因子：
4
通讯作者：
N. Iverson;R. W. Baker;T. Hooyer
中科院分区：
文献类型：
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作者：
N. Iverson;R. W. Baker;T. Hooyer
冰下沉积物的变形可能对更新世冰盖的地貌效应和动力学产生了深远的影响，但有关此类沉积物流变学的数据很少且相互矛盾。环剪切装置提供了一种系统研究冰碛物机械性能的方法，该装置以可变速率将大型环形样本剪切至高应变。该设备的特殊功能可以连续观察剪切应变的分布、测量垂直于剪切方向的局部应力以及隔离壁效应。到目前为止，已经测试了一种线性粘性腻子和两种具有不同粘土含量（按重量计 4% 和 32%）的耕作物。正如预期的那样，对耕耘物的实验表明，分散的粘土矿物的存在显着降低了耕耘物的残余强度和水力扩散率。粘土还可以减少与晶桥相关的法向应力的空间变化。样本周围的墙壁仅支持总剪切阻力的 9-17%。应变集中在两个收银台中，但不在线性粘性腻子中。收银台中的应变定位表明它们的流变学与线性和宾厄姆粘性模型显着不同。
Deformation of subglacial sediment may have had a profound influence on the geomorphic effects and dynamics of Pleistocene ice sheets, but data that bear on the rheology of such sediment are few and contradictory. A means of studying systematically the mechanical properties of glacial tills is provided by a ring-shear device that shears a large annular specimen to high strains at variable rates. Special features of the device allow continuous observation of the distribution of shear strain, measurement of local stresses normal to the direction of shear, and isolation of wall effects. Thus far, a linear-viscous putty and two tills with different clay contents (4 and 32% by weight) have been tested. The experiments with till indicate, as expected, that the presence of dispersed clay minerals reduces markedly both the residual strength and hydraulic diffusivity of till. Clay also reduces spatial variations in normal stress associated with grain bridges. The walls bounding the specimen support only 9–17% of the total resistance to shearing. Strain was localized in both tills, but not in the linear-viscous putty. Strain localization in the tills indicates that their theology departs significantly from linear- and Bingham-viscous models.