The Effects of Canyon Topography on Dynamic Stress Distribution in Earth Dams

Limitations of computer storage capacity and high costs have generally restricted the use of numerical methods to two-dimensional dynamic analyses of earth dams. However, differences in canyon topographies in which the earth dams have been built may cause various constraining effects. Comparison between results of plane strain and three-dimensional dynamic analyses may reflect the site effects especially in narrow canyons. Consequently, considering the geometry of canyon, one may choose an appropriate method of dynamic analysis. This paper presents the effect of different canyon geometries on amount and distribution of induced dynamic stresses in plane strain and in three-dimensional analyses. These analyses are executed by FLAC2D and FLAC3D for some sections of earth dams with different length to height ratios. It has been shown that the ratios of plain strain to 3D dynamic shear stresses reach their maximum and minimum values in triangular and rectangular shaped canyons, respectively. With complimentary studies the actual seismic behavior of earth dams could be estimated from plane strain dynamic analyses