Modeling the mechanical behavior of coarse-grained soil using additive manufactured particle analogs

Systematic investigation of the effects of individual particle properties, such as shape, size, surface roughness, and constituent materials stiffness, on the behavior of coarse-grained soils requires careful control over the other particle properties. Achieving this control is a pervasive challenge in investigations with naturally occurring soils. The rapid advance of modern additive manufacturing (AM) technology provides the ability to create analog particles with independent control over particle size and shape. This work evaluates the feasibility of the stereolithography (SLA) and polyjet technologies to generate analog particles that can model the mechanical behavior of coarse-grained soils. AM is used to generate equal-sized spheres and analog sand particles from 3D X-ray CT scans of natural rounded and angular sand particles. The uniaxial inter-particle compression, oedometer compression, and shear wave transmission behaviors of the AM particles are investigated and compared to those of glass and steel spheres and natural rounded and angular sand particles. The results indicate that AM can successfully reproduce the shape of natural coarse sand particles. The deformation of micro-asperities was found to influence the contact response of the polyjet AM particles, thus affecting their inter-particle uniaxial compression and oedometer compression response. The contact response of the SLA AM particles was closer to that of glass spheres. Both AM particle types exhibit a dependency of shear wave velocity and shear modulus on mean effective stress that is consistent with that of natural sands.