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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粘土含量对断层泥剪胀和摩擦特性的影响
DOI：
10.1002/essoar.10512743.1
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Ashman I
中科院分区：
文献类型：
--
作者：
Ashman I
成熟的断层岩心由极细、低渗透性、含粘土的泥组成。已知饱和粒状断层材料响应于滑动速度的增加而膨胀，导致可以抑制不稳定性的显著孔隙压力下降。到目前为止，只有在粘土贫乏的断层泥中才测量到渗透性。粘土矿物具有低摩擦强度，并且在先前的实验中，即使是小比例的粘土矿物也被证明会影响断层的摩擦特性。因此，详细记录粘土比例对断层岩摩擦特性和粘性的影响是很重要的。在这项工作中，一套三轴变形实验阐明了饱和的，合成的石英粘土（高岭石）断层泥在有效正应力为60 MPa，25 MPa和10 MPa的摩擦行为。当速度增加10倍时，所有粘土石英含量的断层泥显示出可测量的粘性，粘土贫乏的样品产生了与以前研究相当的变化。峰膨胀没有发生在纯石英泥，而是在含有10至20重量%的粘土的泥。泥质含量的模拟断层泥被发现控制断层泥的摩擦强度和滑动的稳定性。在~ 40wt%粘土时，发生了从强的、不稳定滑动的石英为主的断层泥到弱的、但稳定滑动的粘土为主的断层泥的过渡。这些结果表明，在低渗透率，粘土丰富的断层带，孔隙体积的增加可能会产生孔隙流体压力瞬变，有助于逮捕地震成核或潜在的促进持续缓慢滑动。
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 only 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 behaviour and dilatancy of fault rocks. In this work, a suite of triaxial deformation experiments elucidated the frictional behaviour of saturated, synthetic quartz-clay (kaolinite) fault gouges at effective normal stresses of 60 MPa, 25 MPa 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 20 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.