A “principal stress cap” model for stresses in a circular silo with an off-centre circular core: Finite core models, including filled silos, incipient flow and switch stresses

• Silos with offset cores have been modelled.
• Incipient flow and switch stress have been simulated.
• Passive, convex and active, concave principal stress caps are modelled.
• Wall stresses give a poor indication of the underlying stress field.
• Large wall normal angles and high eccentricities are not viable in deep beds.

Stresses have been modelled in a silo with offset centre of stress and finite circular core, using the methodology developed by Matchett et al. (2015). Several types of core-annulus stress interactions have been proposed and some of the problems in the original Virtual Core model have been ameliorated. However, the selection of the most appropriate model is limited by lack of data on internal stress distributions within silos and the observation that different internal structures can give similar wall stress values.Passive systems with convex stress cap and active stress systems with concave stress cap have been modelled. In order to keep wall shear stresses and internal stresses below the yield limits, the model suggests that deep, completely filled silos would have very small values of wall arc normal angles, βc and βw, and stress eccentricity, Ecc. Deep, filled silos with high stress eccentricity and large wall normal angles are not viable.Incipient flow and the stress switch have been simulated. Output data suggest wide variation in wall stresses both axially and azimuthally are possible, at high stress eccentricities, which would have structural implications.

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