Assessment of the seismic performance of a bituminous faced rockfill dam Matteo Albano a,b,n , Giuseppe Modoni b , Paolo Croce b , Giacomo Russo b a Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605, 00143 Rome, Italy b DiCEM – Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Via G. Di Biasio 43, 03043 Cassino, Italy article info Article history: Received 29 November 2013 Received in revised form 27 August 2014 Accepted 8 April 2015 Available online 4 May 2015 Keywords: Performance Earthquake Rockfill dam Bituminous facing Hazard mitigation Limit states abstract In the attempt to codify a procedure exportable to other similar cases, a thorough investigation of the seismic performance of a bituminous concrete faced rockfill dam built in Italy in the early eighties is herein presented. The dam presents a 90 m tall embankment built in a narrow canyon and is situated in a highly seismic region. The implemented methodology encompasses the indications provided by the most recent literature to point out the problems potentially caused by earthquakes and to account for the paramount factors affecting the response of the dam. Particular attention has been paid to the concept of performance, defining its goals in accordance with the most recent standards and deriving the correspondent limit conditions from observations reported in the literature. In order to optimize the computational effort, dynamic analyses with two and three dimensional finite difference codes have been combined to study the coupled response of the embankment, rocky foundation and bituminous facing. After validating the numerical models with centrifuge tests performed on small scale models of the embankment, the performance of the dam has been investigated with reference to a number of possible scenarios focusing on the amplification spectra, the deformation of the embankment and the integrity of the bituminous lining. & 2015 Elsevier Ltd. All rights reserved. 1. Introduction Since it is not possible to prevent earthquakes from occurring, quantification and mitigation of the seismic hazard is the only possible countermeasure to reduce the casualties, deaths, injuries and property damages, periodically caused by these events. Taking advantage of the considerable expertise matured in the past decades, a robust engineering practice has already been imple- mented for the design, assessment and rehabilitation of buildings and more and more specific requirements are being steadily introduced in the current structural codes [1–3]. Unfortunately the same level of standardization has not been attained yet for earth and rockfill dams, mostly due to the fact that each dam is a unique prototype characterized by its specific geometry, materials and local geological conditions [4,5]. Qualita- tive descriptions can be found of the possible failure mechanisms taking place during earthquakes [6,7] but methodologies driving to a quantitative risk assessment have not been defined. Never- theless, the assessment of the seismic performance and the planning of rehabilitation works represent compulsory duties for the engineers faced with the design and management of dams located in highly seismic regions. This duty becomes by far more complex for dams built in old ages and still operating. In fact, while the geometry, the structural arrangement and the materials of new structures can be designed rather freely and controlled throughout construction, the proper- ties of existing dams are often not known and can be hardly modified. It must be additionally considered that a large part of old dams has been designed and built with out of date criteria, not including the most recent findings on the seismic characterization of the sites and on the accuracy of the mechanical models. A methodology encompassing these studies is thus needed to assess the seismic performance of dams and to arrange a plan of economic investments for their current management. With this aim, not only the actual safety conditions of the dam against strong earthquakes should be quantified, but also the effects induced by more frequent and less destructive events should be predicted. The analysis herein presented focuses on rockfill dams coated on their upstream face with bituminous concrete (Bituminous Faced Rockfill Dams or BFRD). Thanks to a number of technical and economical advantages [8,9], about 8% of the large dams built all over the world are made with rockfill [10] and some embankments reach very considerable heights [11]. In comparison with the clay core, the bituminous facings presents the advantage of being applied on the completed embankment, i.e. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/soildyn Soil Dynamics and Earthquake Engineering http://dx.doi.org/10.1016/j.soildyn.2015.04.005 0267-7261/& 2015 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ39 03283288846. E-mail address: matteo.albano@ingv.it (M. Albano). Soil Dynamics and Earthquake Engineering 75 (2015) 183–198