Stresses of Granular Materials in Vertical-Wall Section of Bunkers

The initial stress exerted by bulk solids in the vertical-wall section of a bunker depends on the filling rate of solids. The flow stress is independent of the discharge rate of solids, The initial stress is ordinarily smaller than the flow stress. In the range of high filling rate of solids, however, the initial stress is similar to the flow stress. As a result, the upper bound of stresses can be established only and is estimated from the Janssen equation. In this case, the ratio of the horizontal to vertical stress, k, is represented by the equation k=(1-sin2φ)/(1+sin2φ) where φ is the frictional angle between solids and the vertical bunker walls. The stress ratio is therefore smaller than unity in the vertical-wall section of the bunker. The estimated stresses agree with the present data and early data of other sources. The wall coefficient of friction is the most important of the flow properties of bulk solids.