4 research outputs found
Bio-inspired geotechnical engineering: Principles, current work, opportunities and challenges
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Bio-inspired geotechnical engineering: principles, current work, opportunities and challenges
A broad diversity of biological organisms and systems interact with soil in ways that facilitate their growth and survival. These interactions are made possible by strategies that enable organisms to accomplish functions that can be analogous to those required in geotechnical engineering systems. Examples include anchorage in soft and weak ground, penetration into hard and stiff subsurface materials and movement in loose sand. Since the biological strategies have been ‘vetted’ by the process of natural selection, and the functions they accomplish are governed by the same physical laws in both the natural and engineered environments, they represent a unique source of principles and design ideas for addressing geotechnical challenges. Prior to implementation as engineering solutions, however, the differences in spatial and temporal scales and material properties between the biological environment and engineered system must be addressed. Current bio-inspired geotechnics research is addressing topics such as soil excavation and penetration, soil–structure interface shearing, load transfer between foundation and anchorage elements and soils, and mass and thermal transport, having gained inspiration from organisms such as worms, clams, ants, termites, fish, snakes and plant roots. This work highlights the potential benefits to both geotechnical engineering through new or improved solutions and biology through understanding of mechanisms as a result of cross-disciplinary interactions and collaborations
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Experiments, Simulation, and Optimization of Tree Root Inspired Anchors and Foundations
Geotechnical foundation and anchorage system designs must be adapted to growing and changing loading demands, and the consumption of materials (i.e. steel and concrete) and energy must be reduced. In this dissertation, a bioinspired design approach is developed and employed to seek new solutions to society’s foundation and anchorage needs through the study of the mechanical performance of tree root systems.Beginning with a survey of recent developments in the broader field of bioinspired design, aspects particularly relevant to the exploration of new geotechnical engineering innovations are highlighted. A deeper understanding of a biological system in terms of forms (physical structures), behaviors (processes and mechanisms), and principles (why the forms and behaviors are effective in their context) facilitates the extraction of more general principles that can be transferred between the biological and engineering contexts, circumventing context-specific constraints.
Field vertical pullout tests of three-year-old natural root systems (of Lovell, Marianna, and Myrobalan rootstocks) were performed to develop this understanding of tree root system forms, behaviors, and principles. Direct measurements of force, trunk displacement, and ground displacements, along with photogrammetric reconstruction of 3D root system structure and soil characterization enabled detailed description of the root systems’ mechanical performance. Results showed that the root systems studied are 6-10 times as efficient as a conventional micropile system in developing tensile capacity on a per material volume basis. The 3D root system models were skeletonized as nodes and root branch segments to perform statistical characterization of the architecture of mechanically important structural roots, enabling the development of L-system based tree root system architecture simulation capabilities.
A spectrum of architecture complexity is constructed, ranging from a simplified root analog to an L-system simulation of a root system and a model of an extracted field tree root system specimen. The models are 3D printed and tested in vertical pullout in a dry sand using geotechnical centrifuge modeling to generate information on the features that are most critical for development of efficient anchorage. The most important structural feature affecting vertical pullout capacity was vertically projected area. The force-displacement response of the simplest structure exhibited high initial stiffness and rapid softening, while the more complex models exhibited high peak resistance and residual capacity, indicating tradeoffs between capacity, stiffness, and efficiency in anchor design.
In recognition of the importance of structure deformation mechanisms in the progressive mobilization processes of tree root systems and tree root inspired designs, a soil springs model is developed to investigate the impact of shape and flexibility of embedded structures on pullout behavior. Results reveal a coupling between mobilized bearing and tensile resistances in terms of the rate of development and magnitude. Finally, taking the soil springs model environment and defining the structure curvature as a control input. Optimized nonlinear structure shapes are identified for a broad range of inputs, revealing principles of how to maximize vertical pullout capacity of a nonlinear, flexible embedded structure as a function of the performance demands