USE OF POROSITY IN MODELS OF CONSOLIDATION

Porosity is a fundamental variable used in the small strain theory of consolidation to measure the volume of the pore space in the volume of soil. It is defined as a ratio of the two variables, as opposed to vo lumetric strain, which measures the change in volume of soil only. Por osity increment represents both changes in the pore space and in the v olume of the soil element. Such changes originate by stress changes an d/or by environmental changes (temperature, moisture, or chemistry). T hree different definitions of porosity are commonly adopted in the mod eling of porous deformable materials, originated by the theories of Te rzaghi, Blot, and Hassanizadeh. When changes in the pore volume and th e volume of the material element are of the same order, the difference s in definition of porosities may induce significant differences in va lues of their increments. Lagrangian, material, and spatial porosity i ncrements are defined and compared. The continuity equation used in Te rzaghi's model of consolidation is derived from multiphase mixture the ory to show consistent and inconsistent uses of the porosity increment s.