Force chain structure in a rod-withdrawn granular layer

Abstract

When a rod is vertically withdrawn from a granular layer, oblique force chains can be developed by effective shearing. In this study, the force-chain structure in a rod-withdrawn granular layer was experimentally investigated using a photoelastic technique. The rod is vertically withdrawn from a two-dimensional granular layer consisting of bidisperse photoelastic disks. During the withdrawal, the development process of force chains is visualized by the photoelastic effect. By systematic analysis of photoelastic images, force chain structures newly developed by the rod withdrawing are identified and analyzed. In particular, the relation between the rod-withdrawing force [Formula: see text], total force-chains force [Formula: see text], and their average orientation [Formula: see text] are discussed. We find that the oblique force chains are newly developed by withdrawing. The force-chain angle [Formula: see text] is almost constant (approximately [Formula: see text] from the horizontal), and the total force [Formula: see text] gradually increases by the withdrawal. In addition, [Formula: see text] shows a clear correlation with [Formula: see text].