Hydrostatic stress

In continuum mechanics, a hydrostatic stress is an isotropic stress that is given by the weight of water above a certain point. It is often used interchangeably with 'pressure' and is also known as confining stress, particularly in the field of geomechanics. Its magnitude σ h {displaystyle sigma _{h}} can be given by: In continuum mechanics, a hydrostatic stress is an isotropic stress that is given by the weight of water above a certain point. It is often used interchangeably with 'pressure' and is also known as confining stress, particularly in the field of geomechanics. Its magnitude σ h {displaystyle sigma _{h}} can be given by: where i {displaystyle i} is an index denoting each distinct layer of material above the point of interest, ρ i {displaystyle ho _{i}} is the density of each layer, g {displaystyle g} is the gravitational acceleration (assumed constant here; this can be substituted with any acceleration that is important in defining weight), and h i {displaystyle h_{i}} is the height (or thickness) of each given layer of material. For example, the magnitude of the hydrostatic stress felt at a point under ten meters of fresh water would be where the index w {displaystyle w} indicates 'water'. Because the hydrostatic stress is isotropic, it acts equally in all directions. In tensor form, the hydrostatic stress is equal to where I 3 {displaystyle I_{3}} is the 3-by-3 identity matrix.