Comparison of 2D and 3D Seismic Analysis of Concrete Face Rockfill Dams in Narrow Canyons

Concrete Face Rockfill Dam (CFRD) is a type of rockfill dam with a concrete slab as its impervious part. CFRD is a popular choice in countries with high seismic activity because of its great flexibility under seismic loading and ease of construction especially in rainy regions. Seismic response of rockfill dams is usually evaluated through two dimensional dynamic analyses on the maximum cross-section of the dam. This type of analysis needs sufficient insight regarding the effects of canyon geometry on seismic behavior of dam. This 3D effect is the subject of this study. Using 2D and 3D FEM simulations, we have extracted maximum values of acceleration, displacements and stresses throughout dam body and face slab. Comparison of this results for different canyon geometries has resulted in interesting and useful findings about the effects of canyon geometry on CFRD’s seismic behavior. The results indicate that in canyons wider than 5 times of the dam’s height, 2D and 3D results have good compliance for a middle section of the dam. Results also show that in some geometries especially canyons with mild side slopes, the most critical section of the dam is not necessarily its middle section (section with the max height