Bedding effects in bulk solids in silos: experiments and a polar hypoplastic approach

This paper is concerned with bedding effects in granular bulk solids in silos. Finite element (FE)-analyses were performed for a cylindrical thin-walled steel model silo with imperfections containing dry sand. Numerical calculations were carried out for an axisymmetric case with a polar hypoplastic constitutive relation which can capture the salient properties of granular materials. In the FE-calculations, different types of wall displacements along the silo height were taken into account to model roughly the formation of buckles due to initial imperfections of the silo wall. The effects of the initial void ratio and mean grain diameter of bulk solids, initial stress state, wall roughness, and size and form of buckles were studied. The numerical results clearly show that the modelling of a bedding effect of bulk solids in silos by means of springs is too simple and can lead to strongly unrealistic predictions of the bedding modulus.