Rodrigo Borela Valente
(Advisor: Prof. J. David Frost)
will defend a doctoral thesis entitled,
Micromechanics of passive and active inclusions in granular media
On
Monday, November 29 at 12:30 p.m. In-person: Sustainable Engineering Building (SEB) Room 122 Virtual: https://us02web.zoom.us/j/81698215704?pwd=aURPN3UwbFc3SDdkL1VrSmd1dXFJZ…
Abstract: Passive and active inclusions in granular materials play an increasingly important role in the development of sustainable infrastructure. Passive inclusions, such as geogrids, have been shown to augment service life of roadways and reduce aggregate consumption in pavement base layers. This is possible due to the aggregate-geogrid composite action that results in the redistribution of traffic loads. This study develops three-dimensional models to simulate the cyclic-loading behavior of geogrid-reinforced base layers using the discrete element method (DEM). A new framework to model upper and lower performance bounds is proposed, offering a tool for systematically prototyping new geogrids to optimize pavement performance. The sustainability of linear infrastructure can also be improved with the use of active inclusions for thorough soil exploration and characterization. Self-motile probes are an emergent technology that will enable multidirectional testing of soils in situ. Their locomotion systems have been inspired by annelid peristalsis; the synchronized muscle expansion and contraction employed by earthworms to anchor portions of their bodies and advance into the soil. In this doctoral work, the peristaltic locomotion and the design of burrowing robots is investigated on multiple fronts. First, the soil response to peristaltic waves is studied using DEM to obtain insight into the complex loading path endured by the material and its implications for robot design. Subsequently, the anchorage generated by expanded segments is studied by conducting pullout experiments in sand and further numerical modeling. The effect of robot tip shape in reducing penetration resistance to enable greater advancement into granular beds is then investigated using DEM. Later, the soil response to the anchor–push mechanism is studied by testing robotic prototypes in sand and imaging with X-ray micro-tomography. Finally, a transparent synthetic soil test bed is developed to enable fast prototyping and analysis of burrowing devices with real-time imaging. The findings provide important insight into the soil response to robotic burrowing and how devices can be designed to maximize their advancement into granular media.
Committee:
• Dr. J. David Frost – School of Civil and Environmental Engineering (advisor)
• Dr. Frank L. Hammond III - George W. Woodruff School of Mechanical Engineering
• Dr. Elizabeth Cherry - School of Computational Science and Engineering
• Dr. Duen Horng Chau - School of Computational Science and Engineering
• Dr. Gioacchino Viggiani – L3SR Université Grenoble Alpes
• Dr. Mark H. Wayne – Tensar International Corporation