Safety assessment of existing dams for earthquake conditions

A study was commissioned by the Canadian Electrical Association to define procedures for the seismic safety analysis of existing dams. The guidelines include recommended criteria for seismic safety objectives, methods for estimation of seismic ground motions, analysis procedures for embankment and concrete dams, and methods for making decisions on remedial options. Details are presented on the seismic analysis of embankment dams and foundations. Guidelines are presented in three levels, each level requiring increasing data and analysis detail: screening, site specific investigation, and detailed site investigation. A level one analysis of liquefaction and crest deformation employs standard physical classification and descriptions of embankment materials. Documented field experience can be used together with estimates of peak ground acceleration to establish the seismic stability of the structure. Level two analyses rely on site specific data on soils in the embankment and foundation, often obtained from in-situ testing, and supplemented by analyses of static stresses and dynamic responses of the dam. Level 3 assessments are only required where the potential for liquefaction cannot be determined from level one and two analyses. This type of analysis requires extensive site exploration, laboratory testing and significant computational effort. 29 refs., 3 figs., 2 tabs