A review of design methods for retaining structures under seismic loadings

The earth retaining structures frequently represent key elements of ports and harbors, transportation systems, lifelines and other constructed facilities. Earthquakes might cause permanent deformations of retaining structures and even failures. In some cases, these deformations originated significant damages with disastrous physical and economic consequences. For gravity walls, the dynamic earth pressures acting on the wall can be evaluated by using the Mononobe-Okabe method, while Newmark rigid sliding block scheme is suitable to predict the displacements after the shaking, as demonstrated by several experimental tests. Instead, this simplified approach is not very useful for embedded retaining walls for various reasons. Many researchers are interested to this topic. Advanced numerical analyses, centrifuge modeling, in-situ monitoring of full-scale model are the main developing research activities on this subject. Here, after a brief review on the fundamental seismic earth pressures theories, the application of the pseudostatic approach to the analysis of embedded retaining walls, as prescribed by the European Codes, is highlighted. Finally, some considerations on the certain limitations of this approach is done and the indications given by the latest Italian Building Codes (D.M. 14/01/2008) are summarized. ε – inclination angle of the backfill respect to horizontal β inclination angle of the wall internal face respect to vertical δ – soil-wall friction angle ΨW – dilative component of the soil-wall friction angle α – angle of the planar failure surface respect to horizontal θ – inclination angle of the seismic coefficient k with the vertical. Figure 1 illustrates the assumed symbology. The subscript E indicates the seismic conditions, both for active and passive earth pressure states. In the following, the static loading system is denoted without the subscript.