This Faculty Early Career Development (CAREER) Program grant will promote the scientific understanding of the highly efficient burrowing mechanisms of animals in the natural world. Burrowing organisms can inhabit a wide range of subsurface soil types, and adopt a variety of burrowing strategies such as fracturing, digging, bulk fluidization, localized fluidization, localized grain rearrangement and compaction, facilitated by rhythmically changing their body shape. Several different species such as earthworms and bivalve mollusks possess extraordinary burrowing efficiency compared to most man-made penetrometers. Why the dynamic change in body shape is able to facilitate penetration in particulate soil is still largely unknown. From a geomechanical perspective, this award supports the discovery and fundamental understanding of the interaction between soil and bio-inspired penetrators with dynamic shapes. This research has potential to inspire the development of next-generation, high-efficiency underground construction technologies and versatile small-scale underground penetrometers. Application of these technologies can help reduce energy consumption and improve productivity; and underground sensing networks enabled by bio-inspired burrowing can help monitor the safety of infrastructure. Small, agile underground robots can also be used for normal geotechnical engineering site characterization, and also regions that are normally difficult to reach due to energy and environmental restrictions, such as the exploration of Mars or sites on Earth that are liquefied or damaged due to natural hazards (e.g., earthquakes, landslides, flooding, etc.). In addition, the new knowledge and techniques obtained through this research can be used to develop an understanding of the mechanical interactions between animal and sediment as well as shed light on the ecology and evolution of burrowing organisms. This research will serve as a platform to promote learning, teaching and training: the interdisciplinary and bio-inspired nature of the research is an ideal outreach topic to generate enthusiasm in K-12 students and the public about STEM education and research; the integration of the research approaches and findings into teaching and mentoring will help improve the image of geotechnical engineering and invoke students' interests in interdisciplinary research. The education objective of this project is to utilize this bio-inspired research to educate various audiences, including K-12 students, undergraduate and graduate students, and the general public, on biomimicry research for geotechnical engineering via two major pathways: (1) Partnering with GLBio, a dedicated organization in biomimicry innovation and education, the research outcomes will be disseminated to a broader audience including K-12 students and the general public. In collaboration with GLBio, a mobile interactive demo booth and an adaptable lecture module on the burrowing mechanism will be developed to educate the audience about biomimicry and interdisciplinary research. Outreach activities will be performed through GLBio's network, which includes schools, zoos, and museums in northeast Ohio. (2) A regional alliance for geotechnical engineering education in northeast Ohio (NEOGeo), involving public and private universities as well as local industry partners, will be established to integrate the educational resources and to improve their educational quality. To promote diversity and equality, priority will be given to qualified students from historically underrepresented groups (females and African-Americans), as well as students from low-income families and economically disadvantaged regions when recruiting students for the research program.
The research objective of project is to investigate the interaction between granular materials and bio-inspired penetrators with dynamic shape through integrated experimental and numerical models. The complexity of burrowing lies in the tempo-spatial change in the boundaries between granular materials and the burrower, as well as the solid-flow transition of the granular material. Experimental digital image correlation (DIC) techniques and the numerical discrete element method (DEM) are ideal for characterizing and modeling the granule dynamics, providing key multi-scale information to fully understand this dynamic structure-granule interaction problem. In this research, (1) a simple two-component apparatus utilizing an "artificial muscle" will be designed to mimic the burrowing kinematics of clams; penetration experiments with the artificial clam will provide ground truth multiscale observations of the soil-burrower interaction using DIC; (2) a virtual calibration chamber based on DEM will be developed and validated, and it will be used to investigate more fundamental mechanisms of burrowing at multiple length and time scales, as well as to systematically survey the effects of soil properties, soil stress states and burrower kinematics on burrowing performance. This research will ultimately answer the following questions: 1) Given a certain type of soil, how does the penetrator's changing shape affect the penetration efficiency? 2) Given the penetrator's dynamics and kinematics, how does the penetration efficiency (resistance) correlate to soil properties.
