- Pore water pressure
Pore water pressure refers to the pressure of
groundwaterheld within a soilor rock, in gaps between particles ( pores). For example, in a high permeability soil, the pressure would be close to hydrostatic in no flow conditions. It is also referred to as tensiometerpressure.
Pore water pressure (sometimes abbreviated to "pwp") is vital in calculating soil strengths in
soil mechanics, from Terzaghi's expression for the effective stressof a soil.
BS7755-5.1: 1996 Soil quality — Determination of pore water pressure — Tensiometer method", which is identical with ISO11276:1995, defines pore water pressure as:"the sum of matric and pneumatic pressures"
"The amount of work that must be done in order to transport reversibly and
isothermallyan infinitesimal quantity of water, identical in composition to the soil water, from a pool at the elevation and the external gas pressure of the point under consideration, to the soil water at the point under consideration, divided by the volume of water transported." [BS 7755 1996; Part 5.1]
"The amount of work that must be done in order to transport reversibly and isothermally an infinitesimal quantity of water, identical in composition to the soil water, from a pool at atmospheric pressure and at the elevation of the point under consideration, to a similar pool at an external gas pressure of the point under consideration, divided by the volume of water transported." [BS 7755 1996; Part 5.1]
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