A methodology for the seismic assessment of existing earth dams in Italy

Many earth dams in Italy are located in seismic areas with a seismicity from moderate to high. Moreover, they were built several years ago when the seismic Italian zonation and the construction code were completely different. Their seismic stability has to be assessed in order to ensure the safety of urban areas in the downstream site near the reservoirs. This thesis is aimed at defining a reliable and suitable methodology for the assessment of the ultimate and serviceability limit states of existing earth dams in the light of the new seismic zonation of Italy. The core of the Thesis is a numerical study related to the investigation of the seismic response of earth dams using the finite element method. The first step consisted in the validation of the numerical method. This was performed by comparing the experimental results obtained from two different centrifuge tests with those obtained from the numerical analyses. The main goal was to identify the most relevant influential factors and select the most appropriate constitutive models. Secondly, a parametric study was carried out in order to quantify the influence of each relevant factor. The parametric study concerned two “ideal” existing strategic dams, which represent two typical dam sections in Italy. They are located in the south of Italy, in a site which is exposed to high seismic risk. A deterministic spectrum-compatibility method, customized to the actual Italian regulations on structures and dams (M.LL.PP., 2008 and M.LL.PP., 2014) and to the hazard of the aforementioned site, was adopted for the selection of the input time histories. Two dimensional finite models were set up to reproduce the geometric characterization of the dam structure and its foundation. This parametric study provided a means to assess the effect of different parameters and scenarios on the seismic analysis of dams. To this aim, the results of the two dimensional analyses have been discussed focusing on the role of each factor on the response of earth dam subjected under seismic motion.