On the superposition of work dissipation in Coulomb's soil

This note investigates the applicability of the principle of superposition to the upper bound limit analysis with the Coulomb yield criterion. One app lication of this analysis is in calculation of bearing capacity of foundati ons on "general" soil. It is shown that in this type of plasticity problem, superposition can be applied to the dissipation of work, subject of certai n conditions. It follows that a collapse load for a combination of two arbi trary kinematically admissible velocity fields can be calculated as a weigh ted average of the two collapse loads calculated from the separate fields. Importance of this finding is in simplifications it provides to calculation of collapse loads from complex velocity fields. However, from a practical point of view, cases where superposition cannot be applied have much greate r importance. For these cases it is shown that a combination of the velocit y fields from two kinematically admissible velocity fields sometimes allows the upper bound value of surface traction to be reduced below the values c alculated from the separate fields. (C) 2001 Elsevier Science Ltd. All righ ts reserved.