Localization and instability in sheared granular materials: role of friction and vibration

Kothari, Konik Ramesh

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https://hdl.handle.net/2142/97789 Copy

Description

Title

Localization and instability in sheared granular materials: role of friction and vibration

Author(s)

Kothari, Konik Ramesh

Issue Date

2017-04-26

Director of Research (if dissertation) or Advisor (if thesis)

• Hu, Yuhang
• Elbanna, Ahmed

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Granular materials
• Shear localization

Abstract

Shear banding and stick-slip instabilities have been long observed in sheared granular materials. Yet, their microscopic underpinnings, interdependencies and variability under different loading conditions have not been fully explored. Here, we use a non-equilibrium thermodynamics model, the Shear Transformation Zone theory, to investigate the dynamics of strain localization and its connection to stability of sliding in sheared, dry, granular materials. We consider frictional and frictionless grains as well as presence and absence of acoustic vibrations. Our results suggest that at low and intermediate strain rates, persistent shear bands develop only in the absence of vibrations. Vibrations tend to fluidize the granular network and de-localize slip at these rates. Stick-slip is only observed for frictional grains and it is confined to the shear band. At high strain rates, stick-slip disappears and the different systems exhibit similar stress-slip response. Changing the vibration intensity, duration or time of application alters the system response and may cause long-lasting rheological changes. We analyse these observations in terms of possible transitions between rate strengthening and rate weakening response facilitated by a competition between shear induced dilation and vibration induced compaction. We discuss the implications of our results on dynamic triggering, quiescence and strength evolution in gouge filled fault zones.

Graduation Semester

2017-05

Type of Resource

text

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http://hdl.handle.net/2142/97789

Copyright and License Information

Copyright 2017 Konik Kothari

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