Frictional strength of wet and dry montmorillonite

Journal of Geophysical Research
By: , and 

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Abstract

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, μ, 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 μ 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, μ increased from 0.10 to 0.28 with applied effective normal stress, while for dry samples μ decreased from 0.78 to 0.45. The steady state rate dependence of friction, (a − b), 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.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Frictional strength of wet and dry montmorillonite
Series title Journal of Geophysical Research
DOI 10.1002/2016JB013658
Volume 122
Issue 5
Year Published 2017
Language English
Publisher AGU
Contributing office(s) Earthquake Science Center
Description 18 p.
First page 3392
Last page 3409