Strong sediments at the deformation front, and weak sediments at the rear of the Nankai accretionary prism, revealed by triaxial deformation experiments
Strong sediments at the deformation front, and weak sediments at the rear of the Nankai accretionary prism, revealed by triaxial deformation experiments
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DOI：
10.1002/ggge.20290
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发表时间：
2013-11
期刊：
影响因子：
3.7
通讯作者：
M. Stipp;Malte Rolfs;Y. Kitamura;J. Behrmann;K. Schumann;D. Schulte‐Kortnack;V. Feeser
中科院分区：
文献类型：
--
作者：
M. Stipp;Malte Rolfs;Y. Kitamura;J. Behrmann;K. Schumann;D. Schulte‐Kortnack;V. Feeser
来自南开增生棱镜的19个全圆形岩心样品（IODP Expeditions 315，316和333）从海底以下28-128米深度范围内的实验变形在三轴单元固结和不排水条件下，围压为400-1000千帕，室温，轴向位移速率为0.01-9.0毫米/分钟，轴向压缩应变高达1.64%。尽管粉质粘土样品的成分和粒度分布有很大的相似性，两个不同的“流变组”的区别：第一组显示偏峰值应力后，只有百分之几的压缩应变（10%），或不减弱。这是结构坚固材料的特征。强样品倾向于超固结，并且都来自加积棱柱体趾部的钻探场地，而弱的和正常固结的样品来自进一步向上倾斜的大型断层的直接上盘。来自外来板块的沉积物在结构上也很脆弱。所观察到的力学行为的差异，可能持有理解的应变局部化和脆性断裂的南开增生棱柱体的均匀粉质和粘土质沉积序列的关键。
Nineteen whole‐round core samples from the Nankai accretionary prism (IODP Expeditions 315, 316, and 333) from a depth range of 28–128 m below sea floor were experimentally deformed in a triaxial cell under consolidated and undrained conditions at confining pressures of 400–1000 kPa, room temperature, axial displacement rates of 0.01–9.0 mm/min, and up to axially compressive strains of ∼64%. Despite great similarities in composition and grain size distribution of the silty clay samples, two distinct “rheological groups” are distinguished: The first group shows deviatoric peak stress after only a few percent of compressional strain (10%), or does not weaken at all. This is characteristic of structurally strong material. The strong samples tend to be overconsolidated and are all from the drillsites at the accretionary prism toe, while the weak and normally consolidated samples come from the immediate hanging wall of a megasplay fault further upslope. Sediments from the incoming plate are also structurally weak. The observed differences in mechanical behavior may hold a key for understanding strain localization and brittle faulting within the uniform silty and clayey sedimentary sequence of the Nankai accretionary prism.