Seismic analysis of a zoned earth dam after decades of operation

The seismic safety assessment of zoned earth dams that have been in operation for several decades requires a preliminary evaluation of their pre-seismic behavior through the interpretation of monitoring data and laboratory tests on construction materials, collected throughout the dam's service life. Once it is verified whether any factors have influenced the dam's performance and whether this behavior remains consistent with the original design expectations, the seismic response can be analyzed using either pseudo-dynamic (Newmark-based) or coupled elastoplastic continuum approaches. The most relevant damage mechanisms are those affecting watertightness. Zoned earth dams may develop seismic-induced fractures resulting from sliding through the core or from stress release associated with distributed deformation. Coupled analyses provide fundamental physical insight into the processes governing hydraulic fracturing under both seismic and post-seismic conditions, while pseudo-dynamic methods offer valuable information on potential sliding mechanisms and on whether failure surfaces are likely to propagate through the core. The integration of these two approaches enables a deeper understanding of core vulnerability and improves the overall reliability of seismic safety evaluations. This study explores these aspects through the analysis of the Conza Dam in Italy—a unique case where a major earthquake occurred during construction, and where comparative testing of original and recent materials revealed progressive changes in properties over decades of operation. The combined application of pseudodynamic and coupled dynamic analyses to this case demonstrates their complementarity and effectiveness in predicting potential earthquake-induced damage.