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. 2. Results of the geotechnical and geophysical surveys: MASW tests (a-b, respectively for the Arignano and Briaglia dams) and MRD curves from RC/TS tests, where the filled markers are the TS tests (c-d).

The main results of the geophysical investigations carried out along the dam crest are presented in Fig. 2a-b, respectively for the Arignano and Briaglia dams, in terms of a statistical sample of the shear wave velocity V S profile and minimum misfit profiles (thick lines). Laboratory tests were also conducted on undisturbed samples retrieved from the Briaglia dam. Specifically, the monotonic behaviour of the materials was investigated through isotropically consolidated undrained triaxial tests and oedometric tests. Combined Resonant Column and Torsional Shear (RC/TS) tests were instead carried out to study their mechanical response under cyclic loadings. The results of the tests are presented in Fig. 2c-d in terms of Modulus Reduction and Damping ratio (MRD). The geotechnical models of the structure were built based on the newly conducted tests, together with previously available data. The Arignano dam is constituted by a first layer of sand and silt, followed by 5 m of plastic clays and silts. The structure is supported on a 2 m thick layer of clayey silts, overlying 10 m of fine silty sands. Finally, two layers of soft-to-hard clays are present before reaching the seismic bedrock constituted by a deep layer of marlstones. A summary of the geotechnical parameters is reported in Table 2, whereas the dam model is presented in Fig.3a.

Table 2. Geotechnical parameters adopted for the numerical model of the Arignano dam. Layer z : m V S : m/s k : cm/s φ ': ° c ': kPa MRD curves Dam 1 0.0 ÷ 2.0 150 4·10 -7 21 12 Seed et al. (1986) Dam 2 2.0 ÷ 7.0 160 4·10 -7 21 12 Sun et al. (1988) Found 1 7.0 ÷ 9.0 160 4·10 -7 21 12 Sun et al. (1988) Found 2 9.0 ÷ 19 165 8·10 -7 21 12 Seed et al. (1986) Found 3 19 ÷ 40 350 10 -9 30 1 Sun et al. (1988) Found 4 40 ÷ 51 600 10 -9 30 1 Sun et al. (1988) Bedrock >51 1050 10 -9 - - -