Novel mechanical-dynamical aspects with native Nepalese complex granular slides

We perform chute-flow experiments with native Nepalese fruit seed Champati with epitomic physical properties. Considering supergrain Champatis as a primary material, we add food-grains Gahat and Silam, forming Champati-Gahat and Champati-Silam mixtures with different properties. We study their interactions with structures. Dynamical and depositional characteristics of Gahat and Silam are predictable; however, Champatis exhibit unpredictable hypermobility and superspreading. Mixture mobility is reduced as compared with Champati. Astonishingly, mixtures result in tremendously reduced spreading of Champati but enhanced spreading of Gahat and Silam because Champati provides them with thrust, experiencing anti-thrust in return. We present first demonstration of rapidly intensifying strong phase-separation as mixtures slide down unconstrained slope. Separation-length is enormous for Champati–Silam mixture with Champati-dominant front and strong Silam-dominant rear. Outright spectacular separation evolves between them. Eye-catching phenomenon is that front speeds of Champati-Gahat and Champati-Silam are similar: Gahat applies strong resistance against Champati; Champati incredibly propels Silam. Mixture deposition profiles are in-between their constituents. Fascinating is the substantially higher relative acceleration of Champati in Champati-Silam than in Champati-Gahat flow. Propagation rate of Silam at rear of Champati-Silam is very low with much delayed incipient motion of its rear. After flow-tetrahedral structure interactions, dissipated kinetic energy alters flow dynamics and deposition-pattern. Rearward-facing tetrahedron causes more mass-arrest, increased deposition-depth, backward propagating shocks, and crosswise runout extents but decreased longitudinal extent than forward-facing tetrahedron. Process and civil engineering can substantially benefit from our novel findings. Results contribute to better understanding of hypermobility, superspreading, and phase-separation of some geological flows, including fragmented rock avalanches, and assist in addressing some relevant standing challenges.