In order to research the elastoplastic deformation of sand skeleton under dynamical shear loading some constitutive models are analyzed and built
including the model of the finally or the irreversible deformation in the touched part of particles which maybe crashed; and a method is designed to verify the above model through testing the percent change of masses of different sizes particles before and after sand liquefaction. In order to simulate the nonlinear dynamical volumetric deformation and constitutive relation of shear stress-shear strain during the liquefaction
a time-domain-discrete model of sand diliatancy is suggested; the simplified equation can easily to explain the liquefaction and easily to analyze the dynamical deformations of sand.