Permeability (porous media)

Measure of the ability of a porous material to allow fluids to pass through it Symbol used to represent in situ permeability tests in geotechnical drawings In fluid mechanics, materials science and Earth sciences, the permeability of porous media (often, a rock or soil) is a measure of the ability for fluids (gas or liquid) to flow through the media; it is commonly symbolized as k. Fluids can more easily flow through a material with high permeability than one with low permeability. The permeability of a medium is related to the porosity, but also to the shapes of the pores in the medium and their level of connectedness. Fluid flows can also be influenced in different lithological settings by brittle deformation of rocks in fault zones; the mechanisms by which this occurs are the subject of fault zone hydrogeology. Permeability is also affected by the pressure inside a material. The SI unit for permeability is the square metre (m2). A practical unit for permeability is the darcy (d), or more commonly the millidarcy (md) (1 d ≈ 10−12 m2). The name honors the French Engineer Henry Darcy who first described the flow of water through sand filters for potable water supply. Permeabili