# An experimental investigation of the force network ensemble

## TL;DR

This study experimentally investigates force networks in a cyclically compressed quasi-2D granular system, visualizing force chains and analyzing their statistical properties to compare with theoretical predictions from the force network ensemble theory.

## Contribution

It provides the first detailed experimental visualization and analysis of force network evolution under cyclic loading in a frictionless granular system, validating theoretical models.

## Key findings

- Force chains form and evolve with cyclic compression.
- The contact force distribution matches theoretical predictions.
- Force network properties are statistically characterized.

## Abstract

We present an experiment in which a horizontal quasi-2D granular system with a fixed neighbor network is cyclically compressed and decompressed over 1000 cycles. We remove basal friction by floating the particles on a thin air cushion, so that particles only interact in-plane. As expected for a granular system, the applied load is not distributed uniformly, but is instead concentrated in force chains which form a network throughout the system. To visualize the structure of these networks, we use particles made from photoelastic material. The experimental setup and a new data-processing pipeline allow us to map out the evolution subject to the cyclic compressions. We characterize several statistical properties of the packing, including the probability density function of the contact force, and compare them with theoretical and numerical predictions from the force network ensemble theory.