The Effect of Clay Content on the Dilatancy and Frictional Properties of Fault Gouge
The Effect of Clay Content on the Dilatancy and Frictional Properties of Fault Gouge
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DOI：
10.1029/2022jb025878
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发表时间：
2023-04
期刊：
影响因子：
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通讯作者：
I. Ashman;Daniel R. Faulkner
中科院分区：
文献类型：
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作者：
I. Ashman;Daniel R. Faulkner
成熟的断层岩心由极细、低渗透率、含粘土的泥组成。众所周知，饱和的颗粒状断层材料会随着滑动速度的增加而膨胀，导致显著的孔压下降，从而抑制不稳定性。到目前为止，膨胀性主要是在粘土含量较低的凹坑中测得的。粘土矿物的摩擦强度很低，在以前的实验中，即使是很小比例的粘土矿物也会影响断层的摩擦特性。因此，详细地记录粘土比例对断层岩石的摩擦行为和剪胀的影响是很重要的。在这项工作中，一套三轴变形实验阐明了饱和的合成石英粘土(高岭石)断层泥在有效正应力分别为60、25和10兆帕时的摩擦行为。在速度提高10倍后，所有粘土-石英含量的挖掘物都显示出可测量的膨胀，而粘土含量较低的样品产生了与以前研究类似的变化。在纯石英泥中没有出现峰值膨胀，而在含10~40wt%粘土的泥中出现了峰值膨胀。模拟断层泥的粘土含量控制着断层泥的摩擦强度和滑移稳定性。在∼，40wt%粘土发生了从强烈的、不稳定滑动的石英为主的泥向弱但稳定滑动的粘土为主的泥的转变。这些结果表明，在低渗透、富含粘土的断裂带中，孔隙体积的增加可以产生孔隙-流体压力瞬变，有助于阻止地震成核或潜在地促进持续的慢滑。
Mature fault cores are comprised of extremely fine, low permeability, clay‐bearing gouges. Saturated granular fault materials are known to dilate in response to increases in sliding velocity, resulting in significant pore pressure drops that can suppress instability. Up to now, dilatancy has been measured predominantly in clay‐poor gouges. Clay minerals have low frictional strengths and, in previous experiments, even small proportions of clay minerals were shown to affect the frictional properties of a fault. It is important, therefore, to document in detail the impact of the proportion of clay on the frictional behavior and dilatancy of fault rocks. In this work, a suite of triaxial deformation experiments elucidated the frictional behavior of saturated, synthetic quartz‐clay (kaolinite) fault gouges at effective normal stresses of 60, 25, and 10 MPa. Upon a 10‐fold velocity increase, gouges of all clay‐quartz contents displayed measurable dilatancy with clay‐poor samples yielding comparable changes to previous studies. Peak dilation did not occur in the pure quartz gouges, but rather in gouges containing 10 to 40 wt% clay. The clay content of the simulated gouges was found to control the gouge frictional strength and the stability of slip. A transition occurred at ∼40 wt% clay from strong, unstably sliding quartz‐dominated gouges to weak but stably sliding clay‐dominated gouges. These results indicate that in a low permeability, clay‐rich fault zone, the increases in pore volume could generate pore‐fluid pressure transients, contributing to the arrest of earthquake nucleation or potentially the promotion of sustained slow slip.