Collaborative research: Mapping bed forces to granular flow properties

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Landslides, rock falls, volcanic eruptions, rapid flows of mud, rock, and debris, snow avalanches, and sediment-laden floods are all deadly and costly natural hazards. They all also exemplify what are called natural granular flows. These events are hazardous in part due to their rapid and powerful nature, but also because models used to predict and mitigate their impacts remain imperfect. Seemingly simple questions still pose major challenges to scientists and engineers such as: How large will these events be? How far will they travel? What infrastructure is at risk? This project will investigate how granular flows interact with the things they flow over, with a particular focus on impact forces. The results will aid formulation of more accurate models of granular flow mobility and hazards. Outreach activities will be developed to highlight the excitement and utility of controlled laboratory experiments to study natural hazards. The investigators will develop these in collaboration with pedagogy experts, implement them in 4th-8th grade classrooms, and incorporate them into annual workshops for teachers and as interactive exploration stations at two science museums. The overarching goal of this project is to improve our understanding of the forces imparted by granular flows on their beds. This work is motivated by the hypothesis that many geomorphic processes and associated hazards are driven by the largest bed forces, rather than the mean force. The study will build on advances in granular mechanics and apply a novel blend of discrete element modeling, laboratory experiments, and field measurements to improve our understanding of the full distribution of bed forces. The results will be used to test hypotheses about the sensitivity of bed force distributions to macroscopic flow properties and grain-scale interactions. The findings will be integrated into widely used continuum flow models, and thereby aid the formulation of more accurate models of granular flow hazards and landscape evolution. This award is cofunded by the Geomorphology and Land-use Dynamics (GLD) and Prediction of and Resilience against Extreme Events (PREEVENTS) programs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.