Geomaterials consist of a mixture of solid particles and void space that may be ?lled with ?uid and gas. The solid particles may be di?erent in sizes, shapes, and behavior; and the pore liquid may have various physical and chemical properties. Hence, physical, chemical or electrical interaction - tween the solid particles and pore ?uid or gas may take place. Therefore, the geomaterials in general must be considered a mixture or a multiphase material whose state is described by physical quantities in each phase. The stresses carried by the solid skeleton are typically termed "e?ective stress"...

Geomaterials consist of a mixture of solid particles and void space that may be ?lled with ?uid and gas. The solid particles may be di?erent in sizes, shapes, and behavior; and the pore liquid may have various physical and chemical properties. Hence, physical, chemical or electrical interaction - tween the solid particles and pore ?uid or gas may take place. Therefore, the geomaterials in general must be considered a mixture or a multiphase material whose state is described by physical quantities in each phase. The stresses carried by the solid skeleton are typically termed "e?ective stress"...