زمین

Pore water pressure refers to the pressure of groundwater held within a soil or rock, in gaps between particles (pores). Pore water pressures in below the phreatic level (see alsogroundwater) are measured in piezometers. The vertical pore water pressure distribution in aquifers can generally be assumed to be close to hydrostatic

In the unsaturated zone the pore pressure is determined by capillarity and is also referred to as tension, suction or matric pressure. Pore water pressures under unsaturated conditions (vadose zone) are measured in with tensiometers. Tensiometers operate by allowing the pore water to come into equlibrium with a reference pressure indicator through a permeable ceramic cup placed in contact with the soil

Pore water pressure (sometimes abbreviated to pwp) is vital is calculating the stress state in the ground soil mechanics, from Terzaghi's expression for the effective stress of a soil