Experimental determination of friction coefficient and mobilization force in granular material packed in a cylinder

The case of a cylindrical container filled with granular material is a basic situation where the presence of the wall boundaries induces horizontal pressure, and hence shearing forces caused by friction between the wall of the container and the granular bed in it. It can be found in various engineering applications, e.g. in caissons construction and pile driving, in the design of silos and hoppers, and in space life support systems for water processing where granular material contained in a cylinder is compressed by a spring. When an axial load is applied at one end of the bed, whose both ends are free to move, and increased slowly, the whole granular column starts to slide at a critical load value, called herein the mobilization force. In-situ determination of the friction coefficient and the mobilization force can be used beneficially in the above mentioned practical fields. In this paper, we present experimental methodologies for in-situ measurement of the Coulomb's friction coefficient between the granular material and the wall of the housing cylinder, and the friction mobilization force. We present practically convenient experiments set-ups to measure these parameters. One unique advantage of the method presented is that it allows measurement of the effects of the end support reaction on the mobilization force readily and with desired control. Results from a series of experiments conducted on a bed of activated alumina particles packed in a rigid cylinder are presented along with the simplifying assumptions involved and problems that occurred during the experimental process.