Seismic demand amplification in earth dam by dynamic dam-reservoir interactions (DRI) under near fault pulse type ground motions

Abstract

Past studies investigated the seismic vulnerability of earth dams subjected to far-field earthquakes. Near fault, pulse type motions are known to amplify the seismic demands in long-period structures due to the resonating effect. Thus, this study investigates the seismic demand amplification in an earth dam under near fault pulse type motions, accounting for the dynamic dam-reservoir interactions (DRI). The dam and reservoir are modeled using a Coupled Eulerian-Lagrangian (CEL) approach, with DRI analysis compared to a simplified boundary stress (BS) analysis. A degrading shear modulus captures non-linearity in the geo-materials of the dam, and in the reservoir, it is captured by a pressure-density Hugoniot curve. Pulse and non-pulse motions pertaining to various hazard levels are used as input, and the analysis is performed using the Finite Element (FE) method. The pulse motions induce significant amplifications of the pertinent responses, such as acceleration, shear stress, displacement, and shear strain. Amplifications are more prominent for the latter two, along with considerable residuals (displacement and strain). The profiles of displacement/acceleration along the dam height are shown for the upstream shell, core, and downstream shell. The response-specific amplifications are demonstrated over the dam body. A formal zonation of the amplifications is carried out using a fuzzy clustering algorithm (FCA), which helps summarizing. However, the sloshing behavior of the reservoir remains insensitive to the pulse(s).