Complex engineering projects including large dams require extensive reconnaissance. The study of geological relationships is therefore of major importance, with emphasis on the characteristics of the geological structures. Accordingly, geologic structure affects dam site and reservoir behavior in three ways: (1) its impact on the geomechanical properties of rocks; (2) the importance of geologic structures in the identification and assessment of karst hydrogeology; and (3) its role in seismotectonic and seismic risk analysis of dam projects. Site geology and availability of various geologic data obtained from site investigation are key points in dam construction. Geological structure plays an important role in dam site geology and imposes major limitations on dam behavior during and after construction stages. This role has its own effect on major subjects such as: morphotectonics of rivers; geotechnical properties and engineering geology of dam sites; and hydrogeology of dam abutments and reservoir. The variability and complexity of geological structures regarding their tectonic situation result in different scenarios regarding dam’s behavior. This chapter examines the link between geological structure and dam behavior during and after construction period by describing four dam case examples: two earth (Marun and Gotvand) and two concrete (Karun-1 and -3) dams in Iran.
Part of the book: Dam Engineering