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Overburden pressure, also called lithostatic pressure, confining pressure or vertical stress, is the pressure or stress imposed on a layer of soil or rock by the weight of overlying material. The overburden pressure at a depth z is given by : where ρ(z) is the density of the overlying rock at depth z and g is the acceleration due to gravity. p0 is the datum pressure, the pressure at the surface. In deriving the above equation, we have assumed that gravitational acceleration ''g'' is a constant over ''z'', since it is placed outside the integral. In reality, ''g'' is a (non-constant) function of ''z'' and should appear inside the integral. But since ''g'' varies little over depths which are a very small fraction of the Earth's radius, it is placed outside of the integral in practice for most near-surface applications which require an assessment of lithostatic pressure. In deep-earth geophysics/geodynamics, gravitational acceleration varies significantly over depth and ''g'' may not be assumed to be constant. Compare with the equivalent concept of hydrostatic pressure in hydrodynamics. ==See also== *Sedimentary rock *Effective stress *Pore water pressure 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「overburden pressure」の詳細全文を読む スポンサード リンク
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