Characterization of the 3D printing process for fine-grained soils

The purpose of this study was to explore the 3D printing process of fine-grained soils with a geomechanichal approach. In particular, identifying the factors (including geomechanical characteristics of the soil, geometry of the problem, and 3D printer settings) that influence the behavior of 3D printed samples. To answer this question, three groups of materials differing in mineralogy, consistency limits and consistency, and three types of equipment have been used – an extruder and two 3D printers – to widely investigate the behaviour of the fine-grained soils when subjected to the process. First, the extrusion process has been studied finding that the parameter to take into account to predict the outcome are: the coefficient of consolidation of the soil, the extrusion length and the time of extrusion. Then, a double-porosity model was developed to predict the index properties of 3D printed specimens based on the geotechnical characteristics of the fine-grained soil and the specimens' geometry. This model was validated through its application to specimens with different values of the adimensional spacing between parallel filaments. The research then focuses on the structure of 3D printed clayey soil, examining the relationship between particle arrangements, pore size, orientation, and shape, and the 3D printing process. An experimental campaign was conducted to investigate the evolution of soil tensile state before, during, and after the 3D printing process using oedometric tests. Finally, the experimental campaign, conducted at the Geotechnical Laboratory of the University of Los Andes, sought to accurately reproduce 3D models generated using random field theory using a custom multimaterial 3D printer, finding the relationship between printing velocity, extrusion velocity and area of the nozzle that would guarantee an optimum 3D printing.