Performance-based seismic assessment of earth-fill dams on ophiolitic foundations using nonlinear dynamic finite element modelling

Earthquakes are a major hazard for hydraulic structures, especially earthfill dams. Therefore, seismic stability assessment requires advanced numerical models that capture soil–structure interaction and nonlinear behaviour. This study investigates the seismic performance of the Kayı (Kütahya) clay core earthfill dam using 2-D nonlinear finite element analysis in Plaxis 2D. Twenty real strong ground motion records, scaled from PEER and AFAD databases considering regional characteristics and magnitude–distance compatibility, were used as input motions. The clay core was modelled using the Hardening Soil model under undrained conditions, while other materials were modelled using the Mohr–Coulomb model. The results indicate significant amplification on the crest, with peak accelerations reaching up to 0.85 g and short-period spectral acceleration of 5.0 g (<0.25 s). Crest displacement varied between 8 and 12 cm depending on ground motion characteristics. Although localised excess pore pressure was observed mainly in the clay and upper layers, no global instability developed. However, localised stress concentrations and permanent deformations were observed near the crest and slopes, highlighting strong motion and site effects. These findings emphasise the importance of incorporating regional seismic characteristics and hydro-mechanical effects in dam stability assessment and confirm that nonlinear finite element modelling is a reliable tool for performance-based seismic design.