Editing Overburden pressure

{{short description|Stress imposed on soil or rock by overlying material}}
[[Pressure]] is force magnitude applied over an area. '''Overburden pressure''' is a geology term that denotes the pressure caused by the [[weight]] of the overlying layers of material at a specific depth under the earth's surface.<ref>{{Cite book|last=Baker|first=Richard O.|url=https://www.worldcat.org/oclc/908335687|title=Practical reservoir engineering and characterization|date=2015|others=Harvey W Yarranton, Jerry Jensen|isbn=978-0-12-801823-1|location=Amsterdam|oclc=908335687}}</ref> '''Overburden pressure''' is also called '''lithostatic pressure''', or '''vertical stress.'''<ref name=":0">{{Cite book|last=Khan|first=M. Ibrahim|url=https://www.worldcat.org/oclc/261122682|title=The petroleum engineering handbook : sustainable operations|date=2007|publisher=Gulf Pub|others=Rafiqul Islam|isbn=978-1-60119-627-9|location=Houston, TX|oclc=261122682}}</ref>

In a [[stratigraphic layer]] that is in [[Hydrostatics|hydrostatic]] equilibrium; the overburden pressure at a depth z, assuming the magnitude of the gravity acceleration is approximately constant, is given by:

<math>P(z) = P_0 + g \int_{0}^{z} \rho(z)  \, dz</math>  <ref name=":0" />

where:

* <math>z</math> is the depth in [[Metre|meters]]. 
* <math>P(z)</math> is the overburden pressure at depth <math>z</math>.
* <math>P_0</math> is the [[Atmospheric pressure|pressure at the surface]].
* <math>\rho(z)</math> is the [[density]] of the material above the depth <math>z</math>.
* <math>g</math> is the [[gravity]] acceleration in <math>m/s^2 </math>.

In deep-earth geophysics/geodynamics, gravitational acceleration varies significantly over depth and <math>g</math> should not be assumed to be constant, and should be inside the integral.

Some sections of stratigraphic layers can be sealed or isolated. These changes create areas where there is not static equilibrium. A location in the layer is said to be in under pressure when the local pressure is less than the hydrostatic pressure, and in overpressure when the local pressure is greater than the hydrostatic pressure.<ref name=":0" />

==See also==
*[[Effective stress]]
*[[Lateral earth pressure]]
*[[Pore water pressure]]
*[[Sedimentary rock]]

==References==
{{Reflist}}

{{Geotechnical engineering}}

[[Category:Geophysics]]
[[Category:Soil mechanics]]


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