Unitary Definition of Matric Suction

Abstract

Matric suction or negative matric potential (unit: kilopascal) is the free energy change in a unit volume of water when isothermally transferred from the soil water state to the free water state, and is defined at the soil-water-air representative elementary volume (REV) [Fig.�1(a)]. Matric suction has been widely considered as the most fundamental physical variable governing unsaturated soil behavior such as effective stress, shear strength, swelling pressure, freezing temperature depression, and thermal conductivity. Nevertheless, the prevailing definition of matric suction ( m) as negative capillary pressure or the pressure difference between pore air (ua) and pore water (uw) still bears incomplete physics