Earthworm-inspired robotic locomotion in sand: an experimental study using x-ray tomography

Borela, Rodrigo; Frost, J. David; Viggiani, Gioacchino; Anselmucci, Floriana

doi:10.1680/jgele.20.00085

Cited by 19 publications

(4 citation statements)

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“…Nonetheless, ants achieve stability by gradually removing particles without the need for additional reinforcements-like tunnel linings and rock bolts. These results are applicable to a new class of palm-sized robots, which tunnel into soils (41,42). Heuristics learned from our simulations could aid these robots in finding minimum energy paths through soils.…”

Section: Closurementioning

confidence: 73%

Unearthing real-time 3D ant tunneling mechanics

Macedo

Andò

Joy

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Granular excavation is the removal of solid, discrete particles from a structure composed of these objects. Efficiently predicting the stability of an excavation during particle removal is an unsolved and highly nonlinear problem, as the movement of each grain is coupled to its neighbors. Despite this, insects such as ants have evolved to be astonishingly proficient excavators, successfully removing grains such that their tunnels are stable. Currently, it is unclear how ants use their limited information about the environment to construct lasting tunnels. We attempt to unearth the ants’ tunneling algorithm by taking three-dimensional (3D) X-ray computed tomographic imaging (XRCT), in real time, of Pogonomyrmex ant tunnel construction. By capturing the location and shape of each grain in the domain, we characterize the relationship between particle properties and ant decision-making within an accurate, virtual recreation of the experiment. We discover that intergranular forces decrease significantly around ant tunnels due to arches forming within the soil. Due to this force relaxation, any grain the ants pick from the tunnel surface will likely be under low stress. Thus, ants avoid removing grains compressed under high forces without needing to be aware of the force network in the surrounding material. Even more, such arches shield tunnels from high forces, providing tunnel robustness. Finally, we observe that ants tend to dig piecewise linearly downward. These results are a step toward understanding granular tunnel stability in heterogeneous 3D systems. We expect that such findings may be leveraged for robotic excavation.

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Section: Closurementioning

confidence: 73%

Unearthing real-time 3D ant tunneling mechanics

Macedo

Andò

Joy

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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“…And from there, assuming that the depth of the cavity is known and that the stress state follows geostatic conditions, the unit weight of the material and the lateral earth pressure coefficient can be estimated too, according to the following equations: Fig. 5 Pre-expansion radial stress distribution at the cavity wall for a depth H ¼ 10m and a soil unit weight c ¼ 23:8kN=m 3 . The two simulations were conducted with different lateral earth pressure coefficients K o .…”

Section: Estimation Of Far-field Stressesmentioning

confidence: 99%

“…Moreover, cavity expansion mechanisms are not only used for characterization and design by engineers, but also for burrowing purposes by natural organisms. For instance, roots [1], earthworms [3,11], razor clams [45] and sandfish [22] all use expanding cavities for exploration/navigation toward paths of least resistance or maximum nutrient yield, anchoring during excavation and assessing the mechanical stability of tunnel networks. These similarities between engineered and biological systems have sparked a wave of scientific interest in bio-inspiration applied to geotechnics [23].…”

mentioning

confidence: 99%

Back-calculation of soil parameters from displacement-controlled cavity expansion under geostatic stress by FEM and machine learning

et al. 2022

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Estimating soil properties from the mechanical reaction to a displacement is a common strategy, used not only in in situ soil characterization (e.g., pressuremeter and dilatometer tests) but also by biological organisms (e.g., roots, earthworms, razor clams), which sense stresses to explore the subsurface. Still, the absence of analytical solutions to predict the stress and deformation fields around cavities subject to geostatic stress, has prevented the development of characterization methods that resemble the strategies adopted by nature. We use the finite element method (FEM) to model the displacement-controlled expansion of cavities under a wide range of stress conditions and soil properties. The radial stress distribution at the cavity wall during expansion is extracted. Then, methods are proposed to prepare, transform and use such stress distributions to back-calculate the far field stresses and the mechanical parameters of the material around the cavity (Mohr-Coulomb friction angle $$\phi $$ ϕ , Young’s modulus E). Results show that: (i) The initial stress distribution around the cavity can be fitted to a sum of cosines to estimate the far field stresses; (ii) By encoding the stress distribution as intensity images, in addition to certain scalar parameters, convolutional neural networks can consistently and accurately back-calculate the friction angle and Young’s modulus of the soil.

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“…The stress transfer and pore water distribution, however, are nearly impossible to obtain experimentally. Meanwhile, there is an increasing need to fundamentally understand how roots grow, displace, and stabilize between soil particles, largely motivated by a growing interest in bio-inspired robotics [55,56]. With particle-scale modeling techniques, such as the discrete element method (DEM), mechanical interactions between particles and root branches can be simulated explicitly.…”

Section: -4mentioning

confidence: 99%

Down to the root of vegetated soil: challenges and state-of-the-art

et al. 2022

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Vegetated soil plays an essential role in confronting climate change. It is the host material where inorganic carbon is stored and green infrastructures are built. The expected impacts of climate change, such as extreme wetting-drying cycles, pose an urgent need to understand the interplay between soil deformation, root growth, and water/solute uptake. The key to this challenge lies in the extension of unsaturated soil mechanics to incorporate bio-hydrological processes, such as root growth and water uptake. In this paper, we first provide an overview of the state-of-the-art knowledge of root-zone mechanics and bio-hydrology. We identify the main knowledge gaps and suggest an integrated, bottom-to-top approach to develop a multidisciplinary understanding of soil-water-root interaction. We demonstrate how emerging experimental and numerical methods can be used to study rooted soil under wetting--drying cycles. Although focused on the biophysical processes at root/soil particle scales, we discuss potential up-scaling from the root to the field scale and further research on remaining challenges, such as the microbial activities in vegetated soil.

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Earthworm-inspired robotic locomotion in sand: an experimental study using x-ray tomography

Cited by 19 publications

References 0 publications

Unearthing real-time 3D ant tunneling mechanics

Unearthing real-time 3D ant tunneling mechanics

Back-calculation of soil parameters from displacement-controlled cavity expansion under geostatic stress by FEM and machine learning

Down to the root of vegetated soil: challenges and state-of-the-art

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