Effective stress

Effective stress is a force that keeps a collection of particles rigid. Usually this applies to sand, soil, or gravel. Effective stress is a force that keeps a collection of particles rigid. Usually this applies to sand, soil, or gravel. Karl von Terzaghi first proposed the relationship for effective stress in 1925. For him, the term 'effective' meant the calculated stress that was effective in moving soil, or causing displacements. It represents the average stress carried by the soil skeleton. Effective stress (σ') acting on a soil is calculated from two parameters, total stress (σ) and pore water pressure (u) according to: