Evolution of permeability and microstructure of experimentally-created shear zones in Neogene siliceous mudstones from Horonobe, Japan
Evolution of permeability and microstructure of experimentally-created shear zones in Neogene siliceous mudstones from Horonobe, Japan
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DOI：
10.1016/j.jsg.2013.12.003
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发表时间：
2014-03
影响因子：
3.1
通讯作者：
S. Uehara;M. Takahashi
中科院分区：
文献类型：
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作者：
S. Uehara;M. Takahashi
我们报告的实验测量体积渗透率的变化，由于剪切带，诱导硅质泥岩收集的Koetoi和若奈组，北方北海道，这是已知的断层/裂缝分布和地下水流之间的不同关系。我们通过使用微焦点X射线计算机断层扫描来评估诱导剪切带中的体积变形分布。两种地层样品在达到峰值轴向应力时测得的渗透率变化不同。Koetoi Fm在剪切过程中渗透率没有明显变化。标本，但在若奈FM.试样，体积渗透率增加了2.5倍后，达到峰值应力。这些实验中渗透率变化的差异可以解释两种地层的原位地下水流与裂缝分布之间关系的差异。对X射线图像的分析表明，这种差异应反映在诱导剪切区的体积变形的差异。孔隙塌陷发生在Koetoi组的剪切带中。试样，这导致孔隙度降低，而断裂损伤发展在若奈组。标本，增加孔隙度。这些显微结构的差异可能反映了这些寄主岩石屈服标准的差异。
We report experimental measurements of bulk permeability changes due to a shear zone that is induced in siliceous mudstones collected from the Koetoi and Wakkanai Formations, northern Hokkaido, which are known to show different relationships between fault/fracture distribution and groundwater flow. We evaluate distributions of volumetric deformation in the induced shear zones by using micro-focus X-ray computed tomography. Measured permeability evolution while achieving the peak axial stress for specimens differed for the samples of the two formations. Permeability did not change obviously during shear for the Koetoi Fm. specimens, but in the Wakkanai Fm. specimens, the bulk permeability increased by a factor of 2.5 after reaching the peak stress. The difference in permeability change in these experiments can explain the differences in relationships between in situ groundwater flow and fracture distribution for the two formations. Analyses of the X-ray images reveal that this difference should reflect the differences of the volumetric deformation in the induced shear zones. Pore collapse occurred in the shear zone in the Koetoi Fm. specimen, which leads to porosity reduction, whereas fracture damages developed in the Wakkanai Fm. specimen, increasing porosity. These differences in the microstructure may reflect differences in yielding criteria for these host rocks.