Evaluation of the optimal ground motion intensity measure in the prediction of the seismic vulnerability of earth dams

Abstract

The large majority of existing earth dams were designed with old standards, which often accounted for the effects of earthquakes in a simplified manner. As a result, seismic re-evaluation of these structures is now becoming increasingly important for dam owners. The seismic performance of earth dams can be evaluated at different levels of resolution, typically ranging from simple sliding block analysis, to the use of advanced numerical models. Seismic inputs for these models are typically chosen using code-based or site-specific probabilistic seismic hazard analysis (PSHA). In this study, we analyze the seismic vulnerability of two major earth dams located in Southern Italy, a seismically active area. The two dam systems have different geotechnical characteristics: one of them is founded on potentially liquefiable materials, whereas the other one is not susceptible to liquefaction. Our analyses are based on finite difference numerical simulations using both simplified and advanced constitutive models. Seismic vulnerability of both dams is analyzed by means of analytical fragility functions for various damage mechanisms and ground motion intensity measures (IMs). Such fragility functions are based on nonlinear deformation analyses within the multiple stripe analysis framework. We analyze efficiency and predictability of various IMs in predicting different damage levels and mechanisms. We show that the cumulative absolute velocity is overall the optimal IM in predicting vulnerability of both earth dams. We also analyze the relative importance of PSHA inputs (i.e. alternative ground motion and earthquake rupture forecast models; GMMs and ERFMs, respectively) and numerical models (simplified vs advanced) in the seismic analysis of earth dams by means of tornado diagrams. We show that the choice of GMMs and ERFMs is always more important than that of the constitutive model. However, for dams prone to liquefaction, the choice of the constitutive model has a higher importance than for non-liquefiable earth dams.

Seismic intensity measures and predictive equations for the evaluation of earthquake—induced crest settlements of earth dams

“…As an example, using either field data, relative to postseismic surveys, or numerical predictions, obtained through advanced finite difference or finite element analyses, relative to different types of earth dams, several studies showed the relationship between the permanent crest settlement and the peak ground acceleration or velocity (e.g., Lanzo et al, 6 Lanzo, 7 Park et al, 8 Ghaemi and Konrad, 4 Armstrong et al, 9 Regina et al 10 ), the Arias Intensity (e.g., Yule et al, 11 Sica and Pagano 5 , Brigante and Sica, 12 Pagano and Sica, 13 Lanzo et al, 6 Lanzo, 7 Park et al, 8 Armstrong et al, 9 Cascone et al, 14 Regina et al 10 ), the cumulative absolute velocity (i.e. the integral of the acceleration time-history, e.g., Lanzo et al, 6 Armstrong et al, 9 Regina et al 10 ), the bracketed (e.g., Yule et al, 11 for a threshold acceleration equal to 0.05 g) or the strong motion (Lanzo et al, 6 Armstrong et al, 9 Cascone et al, 14 Regina et al 10 ) duration, the specific energy density (i.e., the integral of the squared velocity time-history; e.g., Lanzo et al 6 ), the destructiveness potential factor (e.g., Cascone et al 14 ), the mean or the predominant period (e.g., Lanzo et al, 6 Ghaemi and Konrad 4 ) and, finally, the pseudo spectral acceleration computed for different vibration periods (e.g., Armstrong et al, 9 Regina et al 10 ).…”

“…As an example, using either field data, relative to postseismic surveys, or numerical predictions, obtained through advanced finite difference or finite element analyses, relative to different types of earth dams, several studies showed the relationship between the permanent crest settlement and the peak ground acceleration or velocity (e.g., Lanzo et al., 6 Lanzo, 7 Park et al., 8 Ghaemi and Konrad, 4 Armstrong et al., 9 Regina et al 10 11 Sica and Pagano 5 , Brigante and Sica, 12 Pagano and Sica, 13 Lanzo et al., 6 Lanzo, 7 Park et al., 8 Armstrong et al., 9 Cascone et al., 14 Regina et al 10 …”

“…), the cumulative absolute velocity (i.e. the integral of the acceleration time‐history, e.g., Lanzo et al., 6 Armstrong et al., 9 Regina et al 10 11 for a threshold acceleration equal to 0.05 g) or the strong motion (Lanzo et al., 6 Armstrong et al., 9 Cascone et al., 14 Regina et al 10 …”

“…), the destructiveness potential factor (e.g., Cascone et al 14 6 Ghaemi and Konrad 4 ) and, finally, the pseudo spectral acceleration computed for different vibration periods (e.g., Armstrong et al., 9 Regina et al 10 …”

Seismic Vulnerability of a Tailings Dam Affected by Subduction Earthquakes

“…Recently, studies have been conducted on the uncertainty analysis of different IMs in predicting damage levels. Regina et al [4], found that the CAV is the optimal IM in predicting the vulnerability of earth dams and the fragility functions based on the CAV have the lowest standard deviation values. Armstrong et al [5], found that the AI was the most efficient IM, however, the CAV has the lower total standard deviation in the evaluation of earth dams.…”