Diane E. Moore
David A. Lockner
Carolyn A. Morrow
2017
<p><span>Montmorillonite is a common mineral in fault zones, and its low strength relative to other common gouge minerals is important in many models of fault rheology. However, the coefficient of friction, </span><i>μ</i><span>, varies with degree of saturation and is not well constrained in the literature due to the difficulty of establishing fully drained or fully dried states in the laboratory. We measured </span><i>μ</i><span> of both saturated and oven-dried montmorillonite at normal stresses up to 700 MPa. Care was taken to shear saturated samples slowly enough to avoid pore fluid overpressure. For saturated samples, </span><i>μ</i><span> increased from 0.10 to 0.28 with applied effective normal stress, while for dry samples </span><i>μ</i><span> decreased from 0.78 to 0.45. The steady state rate dependence of friction, (</span><i>a</i><span> − </span><i>b</i><span>), was positive, promoting stable sliding. The wide disparity in reported frictional strengths can be attributed to experimental procedures that promote differing degrees of partial saturation or overpressured pore fluid conditions.</span></p>
application/pdf
10.1002/2016JB013658
en
AGU
Frictional strength of wet and dry montmorillonite
article