# Force Statistics and Correlations in Dense Granular Packings

## TL;DR

This paper investigates the statistical properties and correlations of contact forces and pressures in dense granular packings, revealing non-random correlations and analyzing measurement errors related to pressure estimation.

## Contribution

It provides new insights into force correlations and pressure measurement accuracy in dense granular media, with experimental proposals for further understanding.

## Key findings

- Non-random force correlations extend over 10-15 particle diameters.
- Pressure measurement errors depend on the number of contacts considered.
- Pressure distributions vary with the size of the pressure cell.

## Abstract

In dense, static, polydisperse granular media under isotropic pressure, the probability density and the correlations of particle-wall contact forces are studied. Furthermore, the probability density functions of the populations of pressures measured with different sized circular pressure cells is examined. The questions answered are: (i) What is the number of contacts that has to be considered so that the measured pressure lies within a certain error margin from its expectation value? (ii) What is the statistics of the pressure probability density as function of the size of the pressure cell? Astonishing non-random correlations between contact forces are evidenced, which range at least 10 to 15 particle diameter. Finally, an experiment is proposed to tackle and better understand this issue.