Confined granular packings: structure, stress, and forces

TL;DR

This study uses large-scale simulations to analyze the structure and stress distribution in static granular packings within cylindrical containers, comparing different construction methods and testing classical theories.

Contribution

It provides new insights into how packing methods affect stress profiles and force distributions, validating and challenging aspects of Janssen's theory.

Findings

Vertical stress becomes depth-independent in deep piles.

Most particle-wall tangential forces are near Coulomb failure, supporting Janssen's theory.

Force distributions decay exponentially at large forces.

Abstract

The structure and stresses of static granular packs in cylindrical containers are studied using large-scale discrete element molecular dynamics simulations in three dimensions. We generate packings by both pouring and sedimentation and examine how the final state depends on the method of construction. The vertical stress becomes depth-independent for deep piles and we compare these stress depth-profiles to the classical Janssen theory. The majority of the tangential forces for particle-wall contacts are found to be close to the Coulomb failure criterion, in agreement with the theory of Janssen, while particle-particle contacts in the bulk are far from the Coulomb criterion. In addition, we show that a linear hydrostatic-like region at the top of the packings unexplained by the Janssen theory arises because most of the particle-wall tangential forces in this region are far from the Coulomb yield criterion. The distributions of particle-particle and particle-wall contact forces $P(f)$ exhibit exponential-like decay at large forces in agreement with previous studies.