Static Stable Arching in Granular Materials Using Trapdoor Discrete-Element Simulations

Arch-like structures form in granular materials when particles flow through an opening. This phenomenon manifests in many engineering applications such as hopper flow, silo discharge, and sand production in wellbores. The formation of a statically stabled arch of connected particles spanning an opening with three different boundary conditions representative of common engineering scenarios is investigated numerically using the discrete-element method. The results are shown in terms of the ability of the particle assemblage to form a statically stable arch and in terms of the contact force evolution between particles. The overall stability of the arch is further assessed by removing particles and reducing friction at contacts until the previously developed statically stable arch collapses. The density of the particle assemblage greatly affects the statically stable arch formation, its shape, its force network structure, and its resistance to collapse. Particle size distribution, especially the proportion of large-size particles, affects the critical size of the trapdoor that enables the formation of a statically stable arch. Several methods of identifying key particles, including a new method, are compared. Insights and potential improvements for studying this phenomenon are shared.