Experiments on granular rheology : effects of particle size and fluid viscosity
Experiments on granular rheology : effects of particle size and fluid viscosity
复制标题
颗粒流变学实验：颗粒尺寸和流体粘度的影响
DOI：
10.1029/2008jb005999
复制
发表时间：
2009
期刊：
影响因子：
--
通讯作者：
& I. Sumita
中科院分区：
文献类型：
--
作者：
N. Higashi;& I. Sumita
为了阐明和比较粒径和流体粘度如何影响颗粒流变性，我们报告了一层干燥和液体饱和玻璃微珠（断层泥的简化模型）的剪切实验结果。我们剪切了分选的玻璃微珠，并测量了由于粘滑行为而波动的应力的时间变化。研究发现，由于静压体积摩擦增大，应力降和滑移重现间隔随着颗粒尺寸的增大而增大。不同粒径的应力-时间序列数据形式不自相似；随着颗粒尺寸的增大，形状呈锯齿状变化，这可以用两个新定义的无因次数来表征。此外，我们发现随着颗粒尺寸的增大，从恒定滑移速度到恒定应力降时间有一个连续的转变。我们还利用剪切玻璃微珠的延时图像确定了剪切带宽度，并发现组成剪切带的颗粒数量随着颗粒尺寸的减小而减少。当玻璃微珠被粘性液体饱和时，润滑使其流变学由摩擦变为粘性，滑移重现间隔增大，这些特性可用于区分粒径效应。在一个固定的加载速率下，有一个粘度，使剪切所需的应力最小，在这个粘度下，我们可以分离摩擦和粘性制度。
We report the results of shear experiments of a thick layer of dry and liquid‐saturated glass beads, a simplified model of fault gouge, in order to clarify and to compare how the particle size and fluid viscosity affect the granular rheology. We sheared sorted glass beads and measured the temporal variation of stress that fluctuates owing to stick‐slip behavior. We found that the stress drop and slip recurrence intervals increase with the particle size because of larger static bulk friction. The forms of stress‐time series data for different particle size are not self‐similar; the form changes toward a sawtooth‐like temporal variation as the particle size increases, which can be characterized using two newly defined dimensionless numbers. In addition, we show that there is a continuous transition from constant slip velocity toward constant stress drop time as the particle size increases. We also determined the shear band width using the time‐lapsed images of the sheared glass beads and found that the number of particles comprising the shear band decreases with the particle size. When the glass beads are saturated with viscous liquid, lubrication causes the rheology to change from frictional to viscous and to increase the slip recurrence interval, and these properties can be used to distinguish from the particle size effects. Under a fixed loading rate, there is a viscosity that minimizes the stress needed for shearing, at which we can separate the frictional and viscous regimes.