Drag force on cylindrical intruders in granular media: Experimental study of lateral vs axial intrusion and high grain-polydispersity effects

TL;DR

This experimental study investigates the drag force on cylinders in granular media, comparing lateral and axial intrusion, and examines effects of high grain-polydispersity on force behavior and shear failure phenomena.

Contribution

It provides new experimental data on drag forces in highly polydisperse granular media and compares lateral and axial intrusion regimes with theoretical models.

Findings

Quantitative agreement with theory in lateral intrusion

Observation of force undulations in axial intrusion

Shear failure linked to polydispersity effects

Abstract

We report on experimentally measured drag force experienced by a solid cylinder penetrating a granular bed of glass beads including, specifically, a highly polydisperse sample with grain sizes in the range 1-100 {\mu}m. We consider both cases of lateral and axial intrusion in which the long axis of the cylinder is held horizontally and vertically, respectively. We explore different regimes of behavior for the drag force as a function of the penetration depth. In lateral intrusion, where the motion is effectively quasi-two-dimensional, we establish quantitative comparisons with existing theoretical predictions across the whole range of depths. In axial intrusion, we observe peculiar undulations in the force-depth profiles in a wide range of intrusion speeds and for different cylinder diameters. We argue that these undulations reflect general shear failure in the highly polydisperse sample and can be understood based on the ultimate bearing capacity theory on a semiquantitative level.