An analysis of switch stresses in two-dimensional bunkers

The method of characteristics, used in previous paper 7, 8] to calculate limiting stress fields in two-dimensional bins and hoppers containing granular material, is used to solve the switch stress problem, i.e. to find the stress field associated with a change in state from active to passive. The solution involves a discontinuity which, at the centre-line, is vertical rather than horizontal as has previously been assumed in other analyses. The peak stress does not occur at the transition but below it where the discontinuity reaches the wall.Wall stresses given by the present method are compared with those by the approximate methods of Walker 11], Walter 4], Enstad 5] and Jenike and Johanson 2, 3]. Substantial differences are found in the form of stress distribution and in the location and magnitude of the peak stresses. It is concluded that the approximate methods leave much to be desired.