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 applie ...
, Byerlee's law, also known as Byerlee's friction law concerns the
shear stress
Shear stress (often denoted by , Greek alphabet, Greek: tau) is the component of stress (physics), stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross secti ...
(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
stresses (σ
n) below about 2000 bars (200 MPa) the shear stress increases approximately linearly with the normal stress (τ = 0.85 σ
n, where τ and σ
n is in units of MPa) 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 = 50 + 0.6σ
n), where τ and σ
n are in units of MPa, 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
Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...
takes place.
The law is named after the American geophysicist James Byerlee, who derived it experimentally in 1978.
See also
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Archie's law
In petrophysics, Archie's law is a purely empirical law relating the measured electrical conductivity of a porous rock to its porosity and fluid saturation. It is named after Gus Archie (1907–1978) and laid the foundation for modern well l ...
*
Birch's law
References
Inline citations
General references
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Geophysics
Rheology
Scientific laws
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