Static and seismic passive earth pressure coefficients on rigid retaining structures: discussion

The author needs to be commended for his computational efforts in determining the passive earth pressure coefficients for both the static case as well as in the presence of pseudostatic earthquake forces. The upper bound theorem of limit analysis with the use of a kinematically admissible translational failure mechanism was formed as the basis for solving the problem. In this discussion, the passive earth pressure coefficients given by the author have been compared with those obtained on the basis of the limit equilibrium technique by employing the composite logarithmic spiral failure surface both for the static (Kumar and Subba Rao 1997) and the pseudo-static cases (Kumar 2001). The comparison of all of the results is given in Tables D1 and D2. The two approaches compare well with each other. The passive earth pressure coefficients generated on the basis of the upper bound limit analysis in most of the cases are found to be either almost the same or only marginally greater (for larger values of d) than those computed with the limit equilibrium approach. However, compared to the limit equilibrium technique, the limit analysis has an obvious advantag