In
rheology
Rheology (; ) is the study of the flow of matter, primarily in a fluid ( liquid or gas) state, but also as "soft solids" or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an appl ...
, Byerlee's law, also known as Byerlee's friction law
[
] concerns the
shear stress
Shear stress, often denoted by (Greek: tau), is the component of stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross section. ''Normal stress'', on the ot ...
(τ) required to slide one rock over another. The rocks have macroscopically flat surfaces, but the surfaces have small asperities that make them "rough." For a given experiment and at normal
stress
Stress may refer to:
Science and medicine
* Stress (biology), an organism's response to a stressor such as an environmental condition
* Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...
es (σ
n) below about 2000 bars (200 MPa) the shear stress increases approximately linearly with the normal stress (τ = 0.85 σ
n) and is highly dependent on rock type and the character (roughness) of the surfaces, see
Mohr-Coulomb friction law. Byerlee's law states that with increased normal stress the required shear stress continues to increase, but the ''rate'' of increase decreases (τ = 0.5 + 0.6σ
n), and becomes nearly independent of rock type.
[
]
The law describes an important property of
crustal rock, and can be used to determine when slip along a
geological fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
takes place.
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See also
*
Archie's law
In petrophysics, Archie's law relates the ''in-situ'' electrical conductivity (C) of a porous rock to its porosity (\phi\,\!) and fluid saturation (S_w) of the pores:
:C_t = \frac C_w \phi^m S_w^n
Here, \phi\,\! denotes the porosity, C_t th ...
*
Birch's law Birch's law, discovered by the geophysicist Francis Birch, establishes a linear relation between compressional wave velocity and density of rocks and minerals:
: v_\mathrm = a( \bar M ) + b \rho
where \, \bar M \, is the mean atomic mass in fo ...
References
Inline citations
General references
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Geophysics
Rheology
Scientific laws
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