Liyutan earth core rockfill dam was subjected to some deformation damage in the 9•21 Chi-chi earthquake. The permanent displacement distribution rule of the dam is analyzed for exploring seismic failure mechanism of the dam. Moreover
based on the finite element data smoothing method
the permanent strain of the dam is obtained by processing the monitored displacement data. The results reveal that the permanet deformation point to interval dam body and the dam volume is global contraction under strong earthquke. There are tension strain in the upstream dam body slide along the filter layer beacause the pore water pressure of filter material increase and the effective stress decrease. The borders of dam body and bank slopes suffered from the tension