ABSTRACT
The concept of suction or negative pore water pressure and its components was introduced in Chapter 1. As discussed in section 1.2, total suction has two possible components, matrix suction and solute, or osmotic suction. If they can be separately identified or measured, the two components can be combined to give the total suction, by means of eqn. 1.4d. Usually, the relative humidity corresponding to the matrix suction is indistinguishable from 1.0 (or 100%) and eqn. 1.4d reduces to eqn. 1.4e, or more formally:
(ua − uw)total = Rθ logeHs (1.4e)
There are many methods available for measuring matrix, solute or total suction, depending on the range of suctions involved and the relative importance of the two components. Some of the methods were originally used to measure the water content of soils, and have had their use extended to measuring suction.
