IWPDF2023

On the Dynamics of a Granular Medium Subjected to Multiple Impact Loads

K. Uenishi 1 , 2 , ∗ , Y. Kato 2

1 Department of Advanced Energy, The University of Tokyo, Kashiwa 277-8561, Japan 2 Department of Aeronautics and Astronautics, The University of Tokyo, Bunkyo 113-8656, Japan

∗ uenishi@k.u-tokyo.ac.jp

Keywords: Stress transfer in granular media, Granular collapse, Granular buckling.

Fracture and collapse of granular materials may be observed in a variety ofengineering applications, including earthquake-induced slope failures, debris flows, as well ascontrolled surface fracturing of asteroids due to impact loads given during sample-returnspacecraft missions. However, as stated in our previous study [1, 2], the mechanical propertiesof granular materials, especially, granular fracture dynamics, have not been completelyunderstood yet. So far, using the experimental tech nique of dynamic photoelasticity inconjunction with high-speed video cameras, we have recorded dynamic stress transfer andwave / fracture development in two-dimensional granular media. Each granular medium, madeof penny-shaped birefringent polycarbonate particles, has been placed on a rigid horizontalplane with some inclination (slope) angle and subjected to a single dynamic im pact load on itstop free surface. From the experimentally recorded transient particle motion and dynamic stressdevelopment, we have found two distinct failure patterns: (1) complete collapse or mass flowcaused by unidirectional (force-chain-like) stress transfer; and (2) toppling-type sep aration ofthe slope face of the medium due to widely spreading multi-dimensional waves [1]. In addition,we have examined the buckling phenomena of granular media and evaluated the effect of confinement and material heterogeneities on granular fracture dynamics through experimentalpho toelastic observations and numerical discrete element simulations [2]. In this contribution,we study the dynamic interaction of particle motion induced by multiple impact loads, andfurther conduct laboratory photoelastic experiments. We show how transient particle motion,stress transfer and failure patterns inside a granular medium can change according to thevariation of the dynamic loading conditions. References [1] Uenishi, K., Goji, T. (2018). Dynamic fracture and wave propagation in a granular medium: Aphotoelastic study. Proc. Struct. Int., 13, 769-774. [2] Uenishi, K., Xi, D. (2022). The effect of confinement and material heterogeneities on thedy namics of a granular medium subjected to impact loading. Proc. Struct. Int., 37, 404-409.

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