Pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
is force magnitude applied over an area. Overburden pressure is a geology term that denotes the pressure caused by the
weight
In science and engineering, the weight of an object is the force acting on the object due to gravity.
Some standard textbooks define weight as a vector quantity, the gravitational force acting on the object. Others define weight as a scalar qua ...
of the overlying layers of material at a specific depth under the earth's surface.
Overburden pressure is also called lithostatic pressure, or vertical stress.
In a
stratigraphic layer that is in
hydrostatic equilibrium; the overburden pressure at a depth z, assuming the magnitude of the gravity acceleration is approximately constant, is given by:
Where:
*
is the depth in
meters.
*
is the overburden pressure at depth
.
*
is the
pressure at the surface.
*
is the
density
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...
of the material above the depth
.
*
is the
gravity
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
acceleration in
.
In deep-earth geophysics/geodynamics, gravitational acceleration varies significantly over depth and
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.
See also
*
Effective stress
The effective stress can be defined as the stress, depending on the applied tension \boldsymbol_ and pore pressure p, which controls the strain or strength behaviour of soil and rock (or a generic porous body) for whatever pore pressure value or, ...
*
Lateral earth pressure
Lateral earth pressure is the pressure that soil exerts in the horizontal direction. The lateral earth pressure is important because it affects the consolidation behavior and strength of the soil and because it is considered in the design of geotec ...
*
Pore water pressure
*
Sedimentary rock
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
References
Geophysics
Soil mechanics
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