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Multi-directional Loading of 3D-Printed Tree Root Models using a Six-Axis Robotic Arm


The application of bio-inspiration in geotechnical engineering can help develop more efficient and effective solutions. Biological processes, such as the growth of tree roots, have evolved to accommodate limited resources for growth. Recent work provides evidence that root systems can have a significantly higher axial load capacity per material unit mass or volume than conventional foundation systems such as micropiles. For the work presented in this thesis, two small scale root-inspired models (6-leg and 3-leg), a pile, and a plate anchor were 3D printed and tested under combined loading conditions. The tests were performed using a six-axis robotic arm at 1g in subrounded, loose sand. The results of these tests were compared to assess the performance of the tree root-inspired models relative to more standard shapes. In both vertical and horizontal pullout, the piles had the lowest absolute pullout resistance and the plate anchors the highest. The results showed the mobilization of peak capacities at smaller displacements as the pullout angle became more vertical. After normalizing the results by volume, the tests indicate a greater material efficiency in the tree root model with 6 legs relative to the plate, the pile, and the 3 leg models for most directions of loading. The pile gradually increased peak capacity as the pullout angle approached horizontal, nearly matching in material efficiency with the 6-leg model for the horizontal load test. The results suggest that tree-root inspired shapes may provide anchorage with lower material use than traditional practice. In addition, the results of this study show that 1g tests using a robotic arm be used to explore the behavior of soil-structure interaction problems.

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