Nonlinear FEM Analysis of the Seismic Behavior of the Menta Bituminous-Face Rockfill Dam

Abstract

Large embankment dams are characterized by highly nonlinear material behavior. A main challenge to the numerical investigations of such type of dams is the proper selection of constitutive material models and of the required laboratory and field investigations and tests. It is equally important to model realistically the compaction of the fill layers to account for the pre-consolidation effects that fill material undergoes. This paper presents a FEM nonlinear static and seismic analysis of Menta Dam which is located in Southern Italy and is under operation since 2000. The analysis is aimed at considering in a realistic and precise manner the above-described effects. The FEM model is based on the input data provided in the formulation of Theme B of the 15th ICOLD Benchmark Workshop. The Hardening Soil model combined with the Small Strain Stiffness model is used to simulate the behavior of the rockfill for the considered load combinations. The hydrodynamic pressures caused by the reservoir during earthquake is approximated by means of fluid-structure interaction with incompressible fluid. The foundation is assumed massless. The maximum vertical displacement at the end of the construction is approximately eighty centimeters and is in the central zone of the dam. The first impounding causes re-orientation of the principal stresses in the dam body zone underlying the bituminous face, but it does not entail significant additional displacements. The permanent displacements in case of earthquake are moderate, as the permanent settlements are well within the freeboard of the dam. Based on the results of the analyses performed, recommendations are formulated regarding the constitutive models and the type of analysis to be considered for this dam type.