PSI - Issue 44

Andrea Ciancimino et al. / Procedia Structural Integrity 44 (2023) 323–330 Andrea Ciancimino et al. / Structural Integrity Procedia 00 (2022) 000–000

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The size of the mesh elements is defined as suggested by Kuhlemeyer and Lysmer (1969) to ensure an adequate simulation of the wave propagation phenomena. The numerical simulations comprise a first stage necessary to initialize the geostatic stress state. Then, a hydro-mechanical seepage analysis is performed to define the actual condition of the dam. Finally, a dynamic coupled analysis is carried out to study the seismic response of the dams. Free-field lateral conditions and base absorbing dashpots are activated during the last stage to prevent improper wave reflections (Lysmer and Kuhlemeyer, 1969). 4. Results Fig. 4 reports the results of the numerical analyses for some selected input motions in terms of pore water pressure u w build-up in a point just below the water table (a-b) and crest settlement accumulation (c-d). Both the dams show a significant increase of u w due to the large shear strain levels induced by the seismic action. However, some differences can be observed. The response of the Arignano dam is characterized by an initial u w build-up, followed by a relatively fast dissipation of the excess pore pressure (Fig. 4a). Conversely, the excess pore pressure dissipation is slower for the Briaglia dam, leading to a larger accumulation of u w (Fig. 4b). Such differences can be explained by looking at the characteristics of the materials constituting the two structures. The Arignano dam body is characterized by just a 2 m thick layer of liquefiable materials (i.e. sand and silt), while 7 m of the Briaglia dam is constituted by low-plasticity silts. Additionally, the estimated hydraulic conductivity k of the soils is substantially larger for the material constituting the Briaglia dam (Tables 2-3).

Fig. 4. Results of the numerical analyses for some selected input motions in terms of pore water pressure u w build-up in a point just below the water table and crest settlement w for the Arignano (a-c) and Briaglia (b-d) dams.