Applications of Limit Plasticity in Soil Mechanics

A plane strain formulation of Drucker's perfectly plastic theory for soil is presented. Upper and lower-bound solutions to problems involving the stability of slopes and foundations and the pressures against retaining structures are obtained. The lower-bound solutions are obtained from arbitrary equilibrium states; the upper-bound solutions from kinematic analyses using the plastic stress-strain relations after yield. The results indicate that solutions based on conventional slipsurface analysis may be unsafe. The upper and lower-bound solutions are useful guides in making design decisions.