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

325

3

Fig. 1. Location of small dams in the Piedmont region: purple dots represent earth dams.

Table 1. Seismic vulnerability structures and associated levels of risk.

Vulnerability ( V structure )

Classes of vulnerability

Levels of vulnerability

≤ 1

A B C D E

Negligible

1 ÷ 2 2 ÷ 3 3 ÷ 4

Low (hydraulic leakage into the embankment) Moderate (internal erosion of the embankment) High (internal erosion of the foundation) Maximum (freeboard reduction and overflow)

≥ 5

The index V structure can be obtained by combining four different parameters:

(1)

structure V V V = +

V

V

+

+

condition liquefaction settlement

displacement

where: V condition is associated to the general state of the dam, V liquefaction is the vulnerability due to liquefaction phenomena, and V settlements and V displacements are related to potential crest settlements and possible slope displacements, respectively. The V settlements and V displacements can be computed according to specific empirical relationships developed to predict the expected response of the dams. More details on the method can be found in Cosentini et al. (2020). Based on this approach, 85% of the small earth dams in the Piedmont region were associated with large vulnerability levels. The two earth dams selected for this study, namely the Arignano and Briaglia dams, are characterized by vulnerability levels between high and maximum. The first one was built in the second half of the 19 th century in Arignano (Turin, Italy) and dikes the course of the Rio del Lago stream forming a reservoir with a volume of about 640,000 m 3 . The embankment has a trapezoidal cross-section with a crest 380 m long and 5 m wide, and a height of about 7 m. The second one is located within the municipality of Briaglia (Cuneo, Italy) and it was built at the beginning of the 1990s to retain a reservoir volume of about 59,500 m3 from the Rio del Frocco river. The embankment is characterized by a height of about 11 m and a crest 88.5 m long and 4 m wide. 3. Geotechnical and numerical models of the dams The selected case studies have been the subject of extensive geophysical and geotechnical surveys carried out within the ReSba project (Cosentini et al., 2021). Specifically, the geophysical characterization included the execution of active Multi Channel Analysis of Surface (MASW) tests and single-station Horizontal-to-Vertical Spectral Ratio (HVSR) tests. Additionally, passive 2D array measurements were carried out to investigate the foundation materials up to large depths. Together with non-invasive tests, Down-Hole, seismic cone penetration, and flat-dilatometer tests were also performed.