ABSTRACT
The behavior of some fine-grained soils may be influenced considerably by the amount of soluble salts present in the pore fluid. The amount of soluble salts is often referred to as Salinity, which is the total amount of dissolved salts contained in 1 liter of water. Salinity is also referred to as total dissolved solids (TDS) or soluble salts. In soils, the salts are dissolved in the pore fluid between solid particles. Sea water has a salinity of 35 gm/L and contains sodium and potassium chloride along with other cations. The salinity of the pore fluid may help explain differences in behavior within a soil profile of a deposit. The determination of salt concentration may be especially important for investigations involving marine deposits and near coastal soils. Salts may be leached from marine deposits by infiltrating fresh water after deposition, which can alter their behavior considerably. The amount of salinity in offshore marine deposits may also vary by geographic location as the availability of different salts in sea water may change.
Two methods of determining Pore Fluid Salinity are discussed in this chapter: 1) salinity by refractometer; and 2) salinity by electrical conductivity. Both methods require extraction of the pore fluid from the soil sample, which may be performed either by using a soil press or by centrifuge. Both methods are considered indirect.
