Earthquake Analysis of Arch Dams: Factors to Be Considered

The factors that significantly influence the three-dimensional analysis of arch dams are identified: the semiunbounded size of the reservoir and foundation-rock domains, dam-water interaction, wave absorption at the reservoir boundary, water compressibility, dam–foundation rock interaction, and spatial variations in ground motion at the dam-rock interface. Through a series of example analyses of actual dams, it is demonstrated that (1) by neglecting water compressibility, the stresses may be significantly underestimated for some dams or overestimated for others; (2) by neglecting foundation-rock mass and damping, the stresses may be overestimated by a factor of 2 to 3; and (3) spatial variations in ground motion, typically ignored in dam engineering practice, can have profound influence on the earthquake-induced stresses in the dam. This influence obviously depends on the degree to which ground motion varies spatially along the dam-rock interface. For the same dam, this influence would differ from one earthquake to the next, depending on the location and depth of the causative fault relative to the dam site. How to select damping values for the dam concrete and foundation rock is also addressed.