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Dr. Wei Li Co-Authors Paper in Journal PNAS |

Dr. Wei Li, assistant professor of civil engineering, recently published a paper in Proceedings of the National Academy of Sciences, one of the most prestigious
and highly cited multidisciplinary research journals. This paper introduces a new
tomographic imaging technique to study granular media called Interference Optical
Projection Tomography (IOPT), which was developed during Dr. Li’s postdoc years in
Professor Ruben Juanes’ laboratory at MIT.

We civil engineers work with granular media all the time, from the soils we build
our houses upon to the crushed rocks we add to our concrete. We all know that a granular
medium composed of angular particles is more robust than that composed of round particles.
Yet, the grain-scale interactions among the particles that lead to these dramatically
different behaviors are not always clear. Dr. Li and Dr. Juanes provide a new grain-scale
perspective on this phenomenon using IOPT to reconstruct the force chains—the chains
of contacts among grains where forces are transmitted—in 3D packs of angular particles
and round particles. They show that in response to an increasing vertical load, the
pack of round particles forms intensifying vertical force chains, while the pack of
angular particles forms more interconnected force-chain networks, which are more resistant
to shear failure.
Dr. Li's IOPT can help us better understand the grain-scale underpinnings of landslides
and earthquakes and better engineer granular material used in construction in the
future. This work was featured in MIT News and MIT Spotlight.