Sliding stability analysis of gravity retaining walls using the pseudo-dynamic method

The sliding stability of gravity retaining walls for the dynamic active case is studied using the pseudo-dynamic method. After rectifying the wall inertia equations, the pseudo-static method of Richards and Elms is compared with the present pseudo-dynamic method in the active case. Comparison of the two methods for the same combination of input parameters indicates that the pseudo-static method and the pseudo-dynamic method predict the same value of combined dynamic factor (F-W) for the low range of horizontal seismic acceleration coefficient k(h): However, for higher values of k(h), the pseudo-static method overestimates the value of F-W compared with the pseudo-dynamic method. Using the pseudo-dynamic method, it is observed that the maximum values of the stability factors (the soil active thrust factor F-T, the wall inertia factor F-I and F-W) do not occur simultaneously during the application of input motions. When F-W is at its maximum value (which is the sliding stability criterion), other factors are not at their maximum values, and thus multiplying the maximum of the partial factors causes overestimation of F-W in the pseudo-static method. Comparing the predictions of the pseudo-dynamic method with the experimental results confirms that use of the pseudo-static method for seismic design of retaining walls may be over-conservative, especially for high values of peak ground motions.