Shear fractures in anisotropic ductile materials

An experimental approach

Enrique Gomez-Rivas*, Albert Griera

*Corresponding author for this work

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Analogue models have been used to investigate the influence of planar mechanical anisotropy on the orientation of shear fractures in an elastoviscous-brittle material. Multilayered models consisting of a mixture of plasticine, vaseline and preferentially-oriented paper flakes have been coaxially deformed for this purpose. The evolution of the orientation, length and connectivity of fracture sets has been systematically analysed with progressive coaxial deformation. The experimental results show that the orientation of fractures with respect to the deformation axes depends on the orientation of transverse anisotropy. Two symmetrical sets of shear fractures are formed in models with layering parallel to the extension axis X, while the fracture network is asymmetrical with respect to the deformation axes for cases with oblique anisotropy. The average dihedral angles between fracture sets are higher than 100 degrees, with the obtuse bisector between the two sets oriented perpendicular to layers. The stress fields calculated from fracture data differ from the boundary conditions applied by the deformation apparatus. This misorientation is related to the degree of anisotropy. In models with high oblique anisotropy both fracture arrays rotate in a dextral sense together with layers towards the X-axis, indicating that the presence of a strong anisotropy controls their evolution with progressive deformation. (C) 2011 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)61-76
Number of pages16
JournalJournal of Structural Geology
Volume34
Early online date9 Nov 2011
DOIs
Publication statusPublished - Jan 2012

Keywords

  • shear fracture
  • anisotropy
  • layering
  • fracture orientation
  • stress field
  • multilayer
  • single-crystals
  • deformation experiments
  • vorticity analysis
  • biaxial tests
  • rock masses
  • strain
  • bands
  • brittle
  • fluid
  • zones

Cite this

Shear fractures in anisotropic ductile materials : An experimental approach. / Gomez-Rivas, Enrique; Griera, Albert.

In: Journal of Structural Geology, Vol. 34, 01.2012, p. 61-76.

Research output: Contribution to journalArticle

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title = "Shear fractures in anisotropic ductile materials: An experimental approach",
abstract = "Analogue models have been used to investigate the influence of planar mechanical anisotropy on the orientation of shear fractures in an elastoviscous-brittle material. Multilayered models consisting of a mixture of plasticine, vaseline and preferentially-oriented paper flakes have been coaxially deformed for this purpose. The evolution of the orientation, length and connectivity of fracture sets has been systematically analysed with progressive coaxial deformation. The experimental results show that the orientation of fractures with respect to the deformation axes depends on the orientation of transverse anisotropy. Two symmetrical sets of shear fractures are formed in models with layering parallel to the extension axis X, while the fracture network is asymmetrical with respect to the deformation axes for cases with oblique anisotropy. The average dihedral angles between fracture sets are higher than 100 degrees, with the obtuse bisector between the two sets oriented perpendicular to layers. The stress fields calculated from fracture data differ from the boundary conditions applied by the deformation apparatus. This misorientation is related to the degree of anisotropy. In models with high oblique anisotropy both fracture arrays rotate in a dextral sense together with layers towards the X-axis, indicating that the presence of a strong anisotropy controls their evolution with progressive deformation. (C) 2011 Elsevier Ltd. All rights reserved.",
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note = "This work was financed through the PhD grant BES-2003-0755 to EGR and research project CGL2004-03657, both funded by the Spanish Ministry of Education and Science. We thank J. Carreras and E. Druguet for discussions on various aspects related to this work, to P.D. Bons and M.W. Jessell for many valuable suggestions and to L.M. Casta{\~n}o for her assistance during some of the experiments. We gratefully acknowledge N. Timms and A. Fagereng, whose constructive reviews greatly improved the manuscript, together with the editorial guidance of T.G. Blenkinsop. We would also like to thank G. Zulauf, F. Marques and D. Koehn for their comments to a previous version of the manuscript.",
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N2 - Analogue models have been used to investigate the influence of planar mechanical anisotropy on the orientation of shear fractures in an elastoviscous-brittle material. Multilayered models consisting of a mixture of plasticine, vaseline and preferentially-oriented paper flakes have been coaxially deformed for this purpose. The evolution of the orientation, length and connectivity of fracture sets has been systematically analysed with progressive coaxial deformation. The experimental results show that the orientation of fractures with respect to the deformation axes depends on the orientation of transverse anisotropy. Two symmetrical sets of shear fractures are formed in models with layering parallel to the extension axis X, while the fracture network is asymmetrical with respect to the deformation axes for cases with oblique anisotropy. The average dihedral angles between fracture sets are higher than 100 degrees, with the obtuse bisector between the two sets oriented perpendicular to layers. The stress fields calculated from fracture data differ from the boundary conditions applied by the deformation apparatus. This misorientation is related to the degree of anisotropy. In models with high oblique anisotropy both fracture arrays rotate in a dextral sense together with layers towards the X-axis, indicating that the presence of a strong anisotropy controls their evolution with progressive deformation. (C) 2011 Elsevier Ltd. All rights reserved.

AB - Analogue models have been used to investigate the influence of planar mechanical anisotropy on the orientation of shear fractures in an elastoviscous-brittle material. Multilayered models consisting of a mixture of plasticine, vaseline and preferentially-oriented paper flakes have been coaxially deformed for this purpose. The evolution of the orientation, length and connectivity of fracture sets has been systematically analysed with progressive coaxial deformation. The experimental results show that the orientation of fractures with respect to the deformation axes depends on the orientation of transverse anisotropy. Two symmetrical sets of shear fractures are formed in models with layering parallel to the extension axis X, while the fracture network is asymmetrical with respect to the deformation axes for cases with oblique anisotropy. The average dihedral angles between fracture sets are higher than 100 degrees, with the obtuse bisector between the two sets oriented perpendicular to layers. The stress fields calculated from fracture data differ from the boundary conditions applied by the deformation apparatus. This misorientation is related to the degree of anisotropy. In models with high oblique anisotropy both fracture arrays rotate in a dextral sense together with layers towards the X-axis, indicating that the presence of a strong anisotropy controls their evolution with progressive deformation. (C) 2011 Elsevier Ltd. All rights reserved.

KW - shear fracture

KW - anisotropy

KW - layering

KW - fracture orientation

KW - stress field

KW - multilayer

KW - single-crystals

KW - deformation experiments

KW - vorticity analysis

KW - biaxial tests

KW - rock masses

KW - strain

KW - bands

KW - brittle

KW - fluid

KW - zones

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JO - Journal of Structural Geology

JF - Journal of Structural Geology

SN - 0191-8141

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