Dilatancy of Quartz Gouge in Pure Shear
- B.E. Hobbs and
- H.C. Heard
Published Online: 18 MAR 2013
Copyright 1986 by the American Geophysical Union.
Mineral and Rock Deformation: Laboratory Studies: The Paterson Volume
How to Cite
Raleigh, B. and Marone, C. (1986) Dilatancy of Quartz Gouge in Pure Shear, in Mineral and Rock Deformation: Laboratory Studies: The Paterson Volume (eds B.E. Hobbs and H.C. Heard), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM036p0001
- Published Online: 18 MAR 2013
- Published Print: 1 JAN 1986
Print ISBN: 9780875900629
Online ISBN: 9781118664353
- Rocks—Testing—Addresses, essays, lectures;
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Dilatancy in artificial fault gouge consisting of quartz sand is produced under pure shear loading conditions at shear stresses of about 1/2 the frictional shear failure strength. The gouge, in a layer at 45° to the axis of a confined cylindrical sample, is maintained at constant normal stress and internal pore pressure while increasing the shear stress. Repeated cycles to failure result in compaction of the gouge up to shear strains of about 0.3 and porosity of about 15%, after which the gouge shows porosity increases upon shear and decreases upon unloading. The rate of change of porosity with shear stress, dΦ/dτ, is about 2×10−4MPa−1, at about 45 to 100 MPa effective normal stress, increasing at lower normal stress.
The shear stress at the onset of dilatancy, is nearly independent of normal stress and confining pressure and is considerably lower than has been previously observed. Pure shear loading may be nearer to the conditions for natural loading of strike slip or normal faults than triaxial loading, and we conclude that dilatancy should occur prior to earthquakes in natural fault zones.