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

Collective dynamics of matter with granularity

Granular materials are abundant in the natural and industrial environment. Typical granular materials are collections of inert, passive particles in which the constituent grains of the material are macroscopic; thus they fill space, are athermal, and interact through only local contact forces. This definition can be broadened to include non-inert particles as well-active particles-in which the grains of an active granular material possess an internal energy source which drives motion. Active granular materials are found in many areas of the biological world, from cattle stampedes and pedestrian traffic flow, to the subterranean world of ant colonies and their collective motion within the nest. We study the rheology and dynamics of inert granular material, and an active granular system of collections of fire-ants, which together we call matter with granularity. In both of these systems we observe bifurcations in the force and flow dynamics which results from confinement effects of the effectively rigid granular materials. In inert granular systems, the onset of flow among particles that are closely packed together causes them to dilate as particles must separate away from each other to accommodate flow. Dilation is a property unique to matter with granularity and other complex fluids in which particles interact locally and occupy space. We explore how dilation influences the inert granular system in situations of local and global forcing: drag of an immersed intruder and avalanche flow respectively. We next study collections of fire ants which also interact with each other locally through contact forces and exclude volume. We study the construction of, and locomotion within subterranean tunnels by groups of fire ants. We find that the traffic dynamics of ants within confined tunnels are significantly affected by tunnel diameter. Reducing tunnel diameter increases the formation of traffic jams due to the inability of ants to pass each other easily. However, we show that jamming within tunnels may have beneficial effects on subterranean locomotion. Individual ants jam there bodies against the walls of vertical tunnels to resist falling. From physics studies of fire ant mobility in confined spaces, we show that subterranean tunnel size has a significant effect on the stability and mobility of ants within these environments.PhDCommittee Chair: Daniel I. Goldman; Committee Member: Andrew Zangwill; Committee Member: David L. Hu; Committee Member: Michael A.D. Goodisman; Committee Member: Michael F. Schat

Bridging Walking and Slithering – Stokesian Locomotion

This a peer reviewed 1-page extended abstract for a talk given at the Dynamic Walking conference, 2021Both legged locomotion and slithering motions typically utilize periodic gaits – repeating cycles of body shape change that produce a net motion through the world. Legged locomotion can be viewed from the perspective of piecewise contact constraint formation and removal. Slithering and low Reynolds number swimming operate under continuous constraints of force balance, wherein dissipation removes the ability to accumulate momentum. Here we discuss how to bridge the gap between these domains of motion, thereby, among other benefits, producing models for the space of legged locomotion with slipping. The connective fabric is the use of a “Stokesian”, or “local connection” model.Army Research Office Defense University Research Instrumentation Program grant W911NF-17-1-0243 Army Research Office Multi University Research Initiative grant W911NF-17-1-0306 National Science Foundation Civil, Mechanical and Manufacturing Innovation grant 1825918 D. Dan and Betty Kahn Michigan-Israel Partnership for Research and Education Autonomous Systems Mega-ProjectPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/172173/1/DW2021-1.pdf84b631d7-aa77-4c16-b024-4ad83d186b3cDescription of DW2021-1.pdf : Main documentSEL

Constant speed gaits should work across all speeds

This is a 1-page peer reviewed extended abstract for a talk presented at Dynamic Walking 2021The Stokesian form of the reconstruction equation of Geometric Mechanics arises when the contact forces are so large compared to body inertia that the group momentum decays almost instantaneously. As special case of this occurs when body velocity is constant. In that case it can be shown that for a variety of types of contact friction, as long as all contacts use the same type of friction, time-rescaling the body shape change would produce a geometrically identical motion at a re-scaled speed. The implication of this observation is that if an animal or robot managed to discover a pattern of shape-changes which produces a constant velocity motion, that pattern could be used for every speed. The limiting factor would not be interaction with the environment -- it would be the ability of the body to change its own shape at the desired rates.Army Research Office Defense University Research Instrumentation Program grant W911NF-17-1-0243Army Research Office Multi University Research Initiative grant W911NF-17-1-0306National Science Foundation Civil, Mechanical and Manufacturing Innovation grant 1825918D. Dan and Betty Kahn Michigan-Israel Partnership for Research and Education Autonomous Systems Mega-ProjectPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/172174/1/DW2021-2.pdf84b631d7-aa77-4c16-b024-4ad83d186b3cDescription of DW2021-2.pdf : Main documentSEL

Self-Drying: A Gecko's Innate Ability to Remove Water from Wet Toe Pads

When the adhesive toe pads of geckos become wet, they become ineffective in enabling geckos to stick to substrates. This result is puzzling given that many species of gecko are endemic to tropical environments where water covered surfaces are ubiquitous. We hypothesized that geckos can recover adhesive capabilities following exposure of their toe pads to water by walking on a dry surface, similar to the active self-cleaning of dirt particles. We measured the time it took to recover maximum shear adhesion after toe pads had become wet in two groups, those that were allowed to actively walk and those that were not. Keeping in mind the importance of substrate wettability to adhesion on wet surfaces, we also tested geckos on hydrophilic glass and an intermediately wetting substrate (polymethylmethacrylate; PMMA). We found that time to maximum shear adhesion recovery did not differ in the walking groups based on substrate wettability (22.7±5.1 min on glass and 15.4±0.3 min on PMMA) but did have a significant effect in the non-walking groups (54.3±3.9 min on glass and 27.8±2.5 min on PMMA). Overall, we found that by actively walking, geckos were able to self-dry their wet toe pads and regain maximum shear adhesion significantly faster than those that did not walk. Our results highlight a unexpected property of the gecko adhesive system, the ability to actively self-dry and recover adhesive performance after being rendered dysfunctional by water