3D printable geomaterials
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One of the many attributes of three-dimensional (3D) printing is the ability to produce particles with independent control of morphology and material properties, parameters that are inexorably entwined in naturally occurring geomaterials. In this paper the 3D printing of surrogate granular materials is described, with examples of the particles produced, and results are presented showing their ability to capture real soil behaviour. Three approaches are demonstrated for the 3D generation of model grains. The first method involves the superimposition of a fractal surface with higher level stochastic features on the face of a closed volume, such as a geodesic spheroid. The second method involves the use of Fourier descriptors or fractal geometry generated from two-dimensional (2D) cross-sections and their interpolation to produce simulated geomaterial particles in three dimensions. The third method involves the generation of complex particles by the aggregation of polyhedral elements such as cubes or octahedra which is suitable for the simulation and fabrication of porous or branching particles. Triaxial tests have been performed on particles produced by the second method, which most readily allows input parameters to be obtained from natural geomaterials. Results of these tests show the ability of the printed particles to reproduce soil behaviour, and demonstrate the effect of particle shape on the material response. Finally, applications of the fabrication of surrogate materials by 3D printing are discussed, for use as standardised, printable geomaterials in future up-scaled geotechnical experiments and other geomechanical research.
