Apparent mass of confined big-grained and small-grained granular materials

Abstract

We study the apparent mass versus height profile of monodispersed granular materials confined in a tube for different grain sizes. Uncooked tapioca balls (sago) were poured into the tube by raining method and the masses were measured at the bottom of the cylindrical tube, where the bottom is the receptacle of the electronic weighing scale. This measurement was done for big and for small tapioca balls. The apparent mass measured for big tapioca balls saturates as the filling height is increased. This is a signature of Janssen effect. On the other hand, the granular materials made of small sago balls exhibited possible signs of aging (compaction) as the experiment progresses because the apparent mass first increased and then gradually decreased. These results suggest that the pressure profile is dependent on grain size and on the manner of introducing the grains in the tube.