Seismic stability analysis of liquefiable earthdams

Earthdams constructed from loose to compact, fine to medium sand fills might be susceptible to liquefaction during a seismic event. A deterministic stability analysis has been proposed and applied to such dams in this study.; There are two basic steps in the proposed method. First, the liquefaction triggering of a dam corresponding to a certain design earthquake is studied using the cyclic stress approach. This step involves initial static and dynamic analyses for identifying the regions where liquefaction could be triggered during the earthquake. Second, the overall slope stability under the static condition shortly after the earthquake is evaluated. For the liquefied regions, the residual undrained strength (steady-state strength) and for non-liquefied zones, the drained strength of the soil is applied. The residual undrained strength is determined from two different approaches. The results of these two approaches are compared to assist judgment on the stability of the dam.; The proposed method has been verified by examining its applicability of Lower San Fernando Dam which failed in liquefaction during the 1971 San Fernando earthquake. The proposed method is then applied to a Canadian dam and the results show that this dam is vulnerable to the flow slide type of failure under the design earthquake.; Finally, two remedial measures are considered for the dam which suffers a flow slide type of failure under the design earthquakes. The applied remedial techniques are the use of stabilizing berms and recompaction of the original fill layer of the dam.