The earthquake induced permanent deformation is a key index for aseismic safety evaluation of rockfill dam. In order to calculate the permanent deformation reasonably

both residual volumetric strain and residual shear strain induced by the earthquake loading should be taken into account. For this reason

the method presented by LIU Han-long is modified. In the modified method

the residual volumetric strain is modeled by a shear-dilation-based approach. The derivation of the dilatancy modulus matrix is given in detail; and the calculation parameters and the analysis steps are also introduced. To test the reliability of dilatancy modulus matrix

the permanent deformation mode of a typical element is analyzed

the computed shear strain and volumetric strain are in good coincidence with the theoretical values. After that

the proposed method is used to calculate the earthquake induced permanent deformation of a core rockfill dam and a concrete faced rockfill dam. The computed distributions of the vertical

longitudinal and transversal permanent displacements are studied in detail. By comparing with the measured results

it is found that the dam deformations are mainly residual settlement; and the horizontal displacements are relatively small. It is proved that the proposed method can catch the features of the permanent deformation behavior of rockfill dam and it can give more reasonable results.