Effective Stress and Pore Pressure in Saturated Soils

In a saturated soil with no water movement, equilibrium exists between stresses in the solid and liquid phases. The stress related to the internal forces acting on the contact points of the particles is termed the effective stress whilst the stress within the liquid phase or water is termed pore pressure. The combination of these two stresses represents the total stress at a point. When a saturated soil is subjected to external forces, the state of equilibrium is altered and changes the effective stresses and pore pressures from their initial values to new values. This increase in the pore pressure, called the excess pore pressure, dissipates in time depending on the drainage conditions and permeability of the soil. This pressure dissipation, in turn, causes a reduction in the volume of the soil, which is predicted by a mathematical-physical model called the consolidation analogy.