Dongzhen dam

located in Putian City of Fujian Province

is just in the northern part of South China coastal seismic zone.This dam was built in 1950swhen the seismic fortification intensity standard hasn′t been set in China.The seismic performance of the dam should be assessed according to current standards.Choosing Dongzhen dam as a proto-type and adopting Byrne dynamic pore pressure model

the liquefaction and displacement characteristics of this dam was studied by the finite difference software FLAC3D.Three seismic acceleration time history curves with exceeding probability of 10%、5%and 2%in 50years were selected as input load in order to meet the needs of the anti-seismic design.Results show that the gravel filling in the upstream part liquefies in some domain under seismic load

and the liquefied area increases with the earthquake intensity.But the volume of liquefied area is still relatively small compared to the non-liquefied area.The liquefaction of the gravel filling results in permanent deformation in dam body. The deformation also increases with earthquake intensity.However

the displacement is relatively unimportant except the dam crest.The liquefaction displacement has no fatal impact on the stability of the main dam.This study can throw light on the seismic resistance design and reinforcement of the dam.