Critical-State Shear Strength and Pore Pressure of Granular Materials

Abstract The plane-strain critical-state friction angle is an important soil parameter in the design of geotechnical projects. The static angle of repose, which is the same as the plane-strain critical-state friction angle for normally consolidated cohesionless soil, was measured in the laboratory in this investigation. The experimental results were used to validate the relationship between the static angle of repose and the interparticle sliding friction. This relationship accounts for the dilatancy developed in the plane-strain critical state and its corresponding pore pressure coefficient at constant volume. In order to develop this relationship, the law of conservation of energy and the limit-equilibrium analysis were employed in a bidimensional plane-strain micromechanical model for the granular media in the critical state. The framework described in this paper accounts for the evolution of shearing resistance with porosity and establishes theoretical porosity thresholds for the contractive, dilative, and collapsible behavior. The results produced by the theory developed herein compared well with the present experimental results and those available in the literature.