Mechanical and hydraulic behavior of a rock fracture under shear deformation

Satoshi Nishiyama, Yuzo Ohnishi, Hisao Ito, Takao Yano

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

With regard to crystalline rock that constitutes deep geology, attempts have been made to explore its hydraulic characteristics by focusing on the network of numerous fractures within. As the hydraulic characteristics of a rock are the accumulation of hydraulic characteristics of each fracture, it is necessary to develop the hydraulic model of a single fracture to predict the large-scale hydraulic behavior. To this end, a simultaneous permeability and shear test device is developed, and shear-flow coupling tests are conducted on specimens having fractures with varied levels of surface roughness in the constant normal stiffness conditions. The results show that the permeability characteristics in the relation between shear displacement and transmissivity change greatly at the point where the stress path reaches the Mohr-Coulomb failure curve. It is also found that there exists a range in which transmissivity is not proportional to the cube of mechanical aperture width, which seems to be because of the occurrence of channeling phenomenon at small mechanical aperture widths. This channeling flow disappears with increasing shear and is transformed into a uniform flow. We develop a simulation technique to evaluate the macroscopic permeability characteristics by the lattice gas cellular automaton method, considering the microstructure of fracture, namely the fracture surface roughness. With this technique, it is shown that the formation of the Hagen-Poiseuille flow is affected by the fracture microstructure under shear, which as a result determines the relationship between the mechanical aperture width and transmissivity.

Original languageEnglish
Article number108
JournalEarth, Planets and Space
Volume66
Issue number1
DOIs
Publication statusPublished - Dec 2014

Keywords

  • Constant normal stiffness
  • Fracture surface roughness
  • Hagen-Poiseuille flow
  • Lattice gas cellular automaton
  • Modified cubic law
  • Mohr-Coulomb failure
  • Shear-flow coupling test

ASJC Scopus subject areas

  • Geology
  • Space and Planetary Science

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