Dynamic response of concrete-faced rockfill dams to strong seismic excitation

A dynamic plane-strain finite-element study of the response of a typical 100-m-tall concrete-faced rockfill (CFR) dam to strong seismic shaking is presented. The rockfill is modeled as an equivalent-linear material, whose strain-dependent shear modulus is proportional to the square root of the confining pressure. Coulomb`s friction law governs the behavior of the interface between face slab and dam, and slippage is allowed to occur whenever the seismic shear tractions exceed the pertinent frictional capacity. Two sets of historic accelerograms, with peak ground accelerations (PGA) of about 0.40g and 0.60g, respectively, are used as excitation. Numerical results highlight key aspects of the seismic response of CFR dams with emphasis on the internal forces developing in the slab. It is shown that slab distress may be produced only from axial tensile forces, developing due mainly to the rocking component of dam deformation. For the 0.60g shaking tensile stresses that are much higher than the likely tensile strength of concrete develop in the slab. The presented results do not account for potentially detrimental three-dimensional (3D) narrow-canyon effects.

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