Numerical investigation of particle shape on mechanical behaviour of unsaturated granular soils using elliptical particles.

Graphical abstract Highlights • When saturation degree rises, shear strength of circular particles assembly rises. • For elliptical particles, shear strength rises with the saturation degree then drops. • The highest apparent-cohesion rise takes place for the highest eccentric particles. • Unsaturated assemblies contract more before the phase transfer point at low strains. • The highest coordination number and shear strength occurs at eccentricity 15%. Abstract The unsaturated soils mechanic is of significant importance for understanding and predicting the actual behavior of unsaturated soils in plenty of geo-environmental condition including tailing dams and earth dams during construction and operation, soil slopes, and shallow foundations. In this research, a micromechanical model for unsaturated assemblies composed of elliptical particles is presented so that the effect of capillary force, confining stress, and particle shape on unsaturated granular media behavior is analyzed in the pendular regime. As one of the early attempts, the toroidal liquid bridge for elliptical particles is studied in granular assemblies using modified ELLIPSE program, Discrete Element Method based program. The results show that although the strength of spherical particles grows when the saturated degree increases, the strength of elliptical particles rises and then decreases; however, the friction angle remains almost constant. Furthermore, the highest percentage of apparent-cohesion rise takes place at saturation degree of 10% at the highest eccentricity. As long as the eccentricity increases, the effect of capillary force on shear strength grows continuously. Not only do unsaturated assemblies contract more at low strains, but also they expand more after the phase transfer point at high stains. The assembly composed of particles with eccentricity of 0.15 has the highest coordination number. The coordination number constantly increases with the saturation degree for circular particles. In contrast, for elliptical particles assemblies, when degree of saturation increases, the coordination number increases at the beginning then drops. [ABSTRACT FROM AUTHOR]