According to the characteristics of Iai’s multiple mechanism plasticity model and boundary surface plasticity model

a multiple mechanism boundary surface plasticity model of saturated sand is established. The concept of multiple mechanism is used as a vehicle for decomposing the complex mechanism into a set of simple shear mechanisms defined in one dimensional space. Each virtual simple shear mechanism is simulated by boundary surface plasticity model in the virtual stress and strain space

with which the complexity of getting the scale parameters when each virtual simple shear mechanism is simulated by the modified Masing’s rule in Iai’s multiple mechanism model is avoided. According to a lot of test data

a relation between the liquefaction front parameter and normalized shear work is presented. The effective stress path is well modeled by several parameters. The effect of rotation of principal stress axial directions and large shear displacement of sand in the earthquake induced liquefaction are taken into account at the same time in the model. The computed results are consistent with the laboratory results.