Effects of Dam-Foundation Contact Conditions on Seismic Performance of Concrete Gravity Dams

This paper presents the effects of dam- foundation contact conditions on seismic performance of concrete gravity dams including base sliding. For illustrative purposes, the Oued Fodda concrete gravity Dam, located in Chlef (northwestern Algeria), is selected as an example and linear as well as nonlinear seismic analyses are performed. In addition, a parametric study based on the friction coefficient is carried out. The Druker-Prager and the multilinear kinematic hardening models are employed in the nonlinear analyses for concrete in the dam and rock in the foundation, respectively. The hydrodynamic pressure of the reservoir water is modeled as added mass using the Westergaard approach. The contact interface in dam-foundation interaction is modeled by contact elements which represent the friction contact. Surface-to-surface contact elements based on the Coulomb's friction law are used to describe the friction. These contact elements use a target surface and a contact surface to form a contact pair. Depending on the component effects of strong ground motion and maximum friction stress characterizing the dam-foundation contact conditions, sliding displacement may occur at the interface causing instability of the dam. The results show that the base sliding displacement depend on the value of friction coefficient at the interface zone. Besides, the sliding displacement decreases the principal stresses in the dam as well as the base shear stress.