Terzaghi's principle

rdf:langString Terzaghi's principle

rdf:langString Terzaghi's Principle states that when stress is applied to a porous material, it is opposed by the fluid pressure filling the pores in the material. Karl von Terzaghi's introduced the idea in a series of papers in the 1920s based on his examination of building consolidation on soil. The principle states that all quantifiable changes in stress to a porous medium are a direct result of a change in effective stress. The effective stress, , is related to total stress, , and the pore pressure, , by , where is the identity matrix. The negative sign is there because the pore pressure serves to lessen the volume-changing stress; physically this is because there is fluid in the pores which bears a part of the total stress, so partially unloading the solid matrix from normal stresses. Terzaghi's principle applies well to porous materials whose solid constituents are incompressible - soil, for example, is composed of grains of incompressible silica so that the volume change in soil during consolidation is due solely to the rearrangement of these constituents with respect to one another. Generalizing Terzaghi's principle to include compressible solid constituents was accomplished by Maurice Anthony Biot in the 1940s, giving birth to the theory of poroelasticity and poromechanics.