|
Pore water pressure (sometimes abbreviated to pwp) 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 also groundwater) 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 equilibrium with a reference pressure indicator through a permeable ceramic cup placed in contact with the soil. Pore water pressure is vital in calculating the stress state in the ground soil mechanics, from Terzaghi's expression for the effective stress of a soil. ==General principles== Pressure develops due to: *Water elevation difference, water flowing from higher elevation to lower elevation and causing a velocity head, or with water flow, as exemplified in the Bernoulli's energy equations. *Hydrostatic water pressure, resulting from the weight of material above the point measured. *Osmotic pressure, inhomogeneous aggregation of ion concentrations, which causes a force in water particles as they attract by the molecular laws of attraction. *Adsorption pressure, attraction of surrounding soil particles to one another by adsorbed water films. 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「Pore water pressure」の詳細全文を読む スポンサード リンク
|