Seismic Response Characteristics of Liquefiable Sites with and without Sediment Ejecta Manifestation

Abstract

Dynamic nonlinear effective stress analysis of 45 well-documented liquefaction field case histories provides insights on the seismic response of sites where simplified liquefaction triggering procedures indicated liquefaction effects would be severe but either surface manifestations were not observed or inconsistent amounts of sediment ejecta were observed. The occurrence of sediment ejecta and its severity depend significantly on hydraulic processes after strong ground shaking ceases, which the simplified procedures do not consider. Postshaking advection processes govern the amount of upward seepage–induced artesian flow that determines ejecta severity. The ejecta potential index (EPI) captures these key aspects of the hydraulic processes of liquefaction manifestation. EPI can be sensitive to variables such as hydraulic conductivity, groundwater level, and input ground motions. However, it proves to be a useful index that correlates well to the severity of ejecta manifestation observed in the field case histories. Sites with severe ejecta have high EPI values, and sites without ejecta have low EPI values.