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This content will become publicly available on February 28, 2019

Title: Effect of induced cohesion on stick-slip dynamics in weakly saturated, sheared granular fault gouge

We use three-dimensional discrete element calculations to study stick-slip dynamics in a weakly wet granular layer designed to simulate fault gouge. The granular gouge is constituted by 8000 spherical particles with a poly-disperse size distribution. At very low liquid content, liquids impose cohesive and viscous forces on particles. Our simulations show that by increasing the liquid content, friction increases and granular layer shows higher recurrence time between slip events. We also observe that slip events exhibit larger friction drop and layer compaction in wet system compared to dry. We demonstrate that a small volume of liquid induces cohesive forces between wet particles that are responsible for an increase in coordination number leading to a more stable arrangement of particles. This stabilization is evidenced with two orders of magnitude lower particle kinetic energy in wet system during stick phase. Similar to previous experimental studies, we observe enhanced frictional strength for wet granular layers. In experiments, the physicochemical processes are believed to be the main reason for such behavior, we show however, that at low confining stresses the hydromechanical effects of induced cohesion are sufficient for observed behavior. Our simulations illuminate the role of particle interactions and demonstrate the conditions under whichmore » induced cohesion plays a significant role in fault zone processes, including slip initiation, weakening, and failure.« less
Authors:
 [1] ;  [2] ; ORCiD logo [3] ;  [4] ;  [1]
  1. Swiss Federal Inst. of Technology Zurich (Switzerland); Swiss Federal Laboratories for Materials Science and Technology (Switzerland)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Nevada, Reno, NV (United States)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  4. Pennsylvania State Univ., University Park, PA (United States)
Publication Date:
Report Number(s):
LA-UR-17-30001
Journal ID: ISSN 2169-9313; TRN: US1801874
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Solid Earth
Additional Journal Information:
Journal Volume: 123; Journal Issue: 3; Journal ID: ISSN 2169-9313
Publisher:
American Geophysical Union
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Earth Sciences; Discrete Element Modeling, faulting, effects of fluid
OSTI Identifier:
1423979