Defining Efficient Stress Transfer in Binary Particle Systems Using Numerical Simulation
U.S. Army Engineer Research and Development Center Vicksburg United States
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The influence of particle size distribution on the stress transfer mechanisms occurring in bimodal granular materials was investigated in this study. Efficient stress transfer is achieved when all particles within an assembly contribute to the resistance of applied loads. Both physical and numerical testing methods were employed including consolidated-undrained triaxial testing and numerical modeling using the discrete element method DEM. Materials investigated included ideal spheres of stainless steel, polypropylene and natural materials consisting of sand and silty-clay. Identification of critical mixture proportions according to percolation theory was attempted by examining the macro- and micromechanical response of bimodal distributions that were dominated by one fraction or were approaching the percolation threshold. Research results were inconclusive in validating the original hypothesis when comparing the numerical results to laboratory experiments. However, a relationship between coordination number and assembly stiffness was observed. Factors contributing to increased connectivity can also contribute to increased stiffness and shear strength.
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