Dilatancy of Quartz Gouge in Pure Shear

  1. B.E. Hobbs and
  2. H.C. Heard
  1. Barry Raleigh and
  2. Chris Marone

Published Online: 18 MAR 2013

DOI: 10.1029/GM036p0001

Mineral and Rock Deformation: Laboratory Studies: The Paterson Volume

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

Author Information

  1. Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 1 JAN 1986

ISBN Information

Print ISBN: 9780875900629

Online ISBN: 9781118664353

SEARCH

Keywords:

  • Rocks—Testing—Addresses, essays, lectures;
  • Rock deformation—Addresses, essays, lectures

Summary

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.