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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Fig. 3. Geotecnical models for the Arignano (a) and Briaglia dams (b) (dimensions in m).

The Briaglia dam (Fig.3b) is mainly constituted by silts and clayey silts overlying weathered sandstones supported by a 6.4 m thick layer of clayey silty sands. The foundation material is constituted by 6 m of medium-hard clays overlying the seismic bedrock, constituted by a stiff deposit of marlstone characterized by V S ≈ 1500 m/s. The main parameters of the model are reported in Table 3.

Table 3. Geotechnical parameters adopted for the numerical model of the Briaglia dam. Layer z : m V S : m/s k : cm/s φ ': ° c ': kPa MRD curves Dam 1 0.0 ÷ 4.5 160 10 -9 32 1 RC test - C1 Dam 2 4.5 ÷ 6.8 190 10 -10 32 1 Darendeli (2001) Dam 3 6.8 ÷ 7.6 230 10 -8 38 1 Rollins et al. (1998) Dam 4 7.6 ÷ 14 270 10 -8 35 1 Seed et al. (1986) Found 1 14 ÷ 20 500 5·10 -10 38 1 RC test - C2 Found 2 20 ÷ 30 800 10 -11 34 1 RC test - C3 Bedrock >30 1500 10 -11 - - -

Fully coupled effective stress analyses are carried out through the Finite-Difference code Flac 2D (Itasca C.G.). The adopted constitutive model is elastic-perfectly plastic with a Mohr-Coulomb failure criterion, coupled with a hysteretic formulation to reproduce the degradation of the material stiffness with increasing strain levels. The model parameters are defined based on the geotechnical models previously introduced (Table 2-3). The numerical analyses are performed considering the possible pore water pressure build-up due to the coupling between shear and volumetric strains of granular soils above the volumetric threshold. The latter is modelled in a simplified manner based on the empirical model proposed by Byrne (1991). The seismic input consists of a set of strong motion signals recorded on reference rock-like outcropping conditions and selected from the ITACA archive (Luzi L., 2019) based on the seismicity of the dam sites.