Force chain structure in a rod-withdrawn granular layer

摘要

When a rod is vertically withdrawn from a granular layer, oblique force chains can be developed by effective shearing. In this study, the force-chain structure in a rod-withdrawn granular layer was experimentally investigated using a photoelastic technique. The rod is vertically withdrawn from a two-dimensional granular layer consisting of bidisperse photoelastic disks.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 F-w, total force-chains force F-t, and their average orientation theta are discussed. We find that the oblique force chains are newly developed by withdrawing. The force-chain angle theta is almost constant (approximately 20 degrees from the horizontal), and the total force F-t gradually increases by the withdrawal. In addition, F-t sin theta shows a clear correlation with F-w.