Packing-dependent granular friction exerted on a rod withdrawn from a granular layer: the role of shear jamming

Abstract

Resistance force acting on a rod vertically withdrawn from a granular layer is studied by experiments and numerical simulations. The initial packing fraction of the granular layer is controlled to evaluate the packing dependence of the resistance force. In both experiments and numerical simulations, the frictional resistance force in the steady slipping regime increases as the initial packing fraction is increased. According to the numerical results, the principal reason for the increase of frictional resistance is the increase of normal force acting on the rod. This large normal force stems from the effective solidification of the granular layer which is caused by the shearing induced by the withdrawn rod. Based on this shear-induced solidification, the experimental data are analyzed using a simple 'cylindrical shear-jammed zone' model. Then, the critical divergence of the size of solidified (shearjammed) zone is observed by increasing the initial packing fraction towards the jamming packing fraction.

Force chain structure in a rod-withdrawn granular layer

“…To characterize the shear-induced force-chain structure in the steady withdrawing regime, here, we focus on the relatively late stage, 300 ≤ t ≤ 500 s. Although the initial transient behavior of force chain development is interesting, the steady behavior should be first analyzed to compare the result with previous studies. 13,14 In Ref. 14, the φ 0 -dependent growth of force chains was assumed.…”

“…In a previous work, 14 Furuta et al proposed a model of an effectively solidified zone that can be constructed by obliquely extending force chains. In this experi-pew Force chain structure in a rod-withdrawn granular layer 11 ment, we directly observed the development of oblique force chains.…”

“…This behavior is consistent with the 3D case. 13,14 Regarding image acquisition, although the complete simultaneous data acquisition of both bright-and dark-field images is impossible, we alternately acquired bright-and dark-field images every 3 s. Because the withdrawing rate is very slow, practically simultaneous data acquisition can be achieved by this protocol. Using both bright-and dark-field images, we can measure the force applied to each photoelastic disk.…”

“…13 In their subsequent study, 14 a similar rod-withdrawing experiment was performed by precisely controlling the packing fraction φ of the granular layer using air fluidization and mechanical vibration. 14 In Ref. 14, the divergent behavior of the withdrawing force F w was observed as φ approached its critical value.…”

“…This idea is consistent with the experimental data and is supported by numerical simulations . 14 However, no direct measurement of the corresponding force-chain development has been experimentally carried out.…”