3D Dynamic Response Analysis of the Denis-Perron Rockfill Dam in a Narrow Valley

Seismic analysis of rockfill dams in narrow valleys presents challenges due to complex material behavior, wave propagation, and three-dimensional (3D) site effects. This study investigates these aspects through a combined parametric and validation analysis of the Denis-Perron Dam—the largest rockfill dam in Eastern Canada— instrumental data from earthquakes and ambient vibrations. Progressive modeling in 1D, 2D+, and 3D reveals that valley geometry significantly affects seismic response when the width-to-height ratio (L/H) is below 4. For Denis-Perron (L/H = 2.21), 3D simulations yielded crest amplification factors of 6–8 at the fundamental frequency (~2 Hz) under nonlinear conditions, compared to 4–5 in 2D. Site effects were concentrated in the dam’s upper third. Validation with recordings from the 1999 M5.1 earthquake confirmed the 3D model’s reliability. Simulations of a historical M5.9 event showed that high-frequency Eastern Canadian motions (>10 Hz) reduce—but do not eliminate—3D effects. Beyond technical insights, the study demonstrates the feasibility of advanced 3D dynamic modeling when supported by structured validation, and highlights the importance of high-quality seismic instrumentation for both dam safety and understanding dam–valley interactions. These findings support improved seismic design, safety assessment, and instrumentation strategies for large dams in complex geological settings.