Poorsusega

Poorsusega, or porosity, is a material's property that describes the fraction of its volume occupied by voids or pores. It is dimensionless and usually expressed as a decimal or percent. Porosity can be total, including all voids, or effective (connected) porosity, which governs fluid flow and storage.

Two main types are primary porosity (pores formed with the material's original framework) and secondary porosity (pores created later by processes such as cracking or dissolution). In soils, porosity is also described as macro-pores (drainage and aeration) and micro-pores (water retention).

Porosity is measured by laboratory and field methods. Total porosity can be estimated from bulk density and particle density: n = 1 − (ρb/ρs). Direct measurements use gas pycnometry, mercury intrusion porosimetry, or NMR; field methods include infiltration tests and core analyses to infer connected porosity.

The amount and connectivity of porosity affect a material's ability to store and transmit fluids. In hydrology, porosity determines aquifer storage; in petroleum geology, it influences reservoir capacity; in agriculture, it affects soil water availability and drainage. Porosity and permeability are related but distinct properties: high porosity does not guarantee high permeability if pore throats are small.

Typical values vary widely. Sands often have porosities around 25–50%, gravels higher, clays 30–60%, and carbonates may exceed 50% depending on structure.