Density and compressibility characteristics of air–water mixtures

Abstract

The density and compressibility of miscible and immiscible air–water mixtures are formulated on the basis of the conservation of mass. Boyle's Law accounts for the compressibility of free air and Henry's Law accounts for the amount of air that goes into solution. The rate of air diffusion into water in the soil is used to choose either the case of complete solution or no solution of air. Formulas are given by which it is possible to predict the density and compressibility of the fluid phase of unsaturated soils.The difference between the air and water pressures in a soil is of interest only in the compressibility formulation. It is not necessary nor advisable to use Kelvin's capillary model equation to account for the difference in air and water pressure since it incorporates an unmeasurable variable, and gives rise to an anomaly. It is recommended that a measurable pore pressure parameter, Baw or Bwa be used in the solution of engineering problems.