Abstract: Most of the constitutive model for liquefaction analysis cannot simulate the large post-liquefaction deformation of saturated sand, and there is little research on the nonlinear time-domain large deformation constitutive relationships suitable for seismic response analysis of saturated sand sites. In this paper, a feasible, simple and applicable large deformation constitutive model for time domain analysis is proposed through experimental analysis and theoretical research. The post-liquefaction stress-strain relationships of liquefied sand are obtained based on the undrained cyclic triaxial test data, then loading-reloading rules of large post-liquefaction deformation are proposed. Combined with the effective stress constitutive model based on logarithmic skeleton curve, a constitutive model that can quantitatively describe the large deformation of saturated sand liquefaction is proposed. According to the test results, the constitutive model can simulate small to large deformations from the pre-to post-liquefaction regime of sand. This constitutive model is also implemented to the program Soilresp1D for the dynamic response analysis of liquefiable soil sites. The results show that the time domain nonlinear large deformation unified constitutive model based on the logarithmic dynamic skeleton curve, effective stress-modified logarithmic dynamic skeleton constitutive model and liquefaction large deformation constitutive model can be directly applied to the dynamic response analysis of saturated sand.

Key words: logarithmic skeleton curve, effective stress, liquefaction of saturated sand, loading-unloading rules, large deformation constitutive model