Abstract: The diffusion and redistribution of the excess pore pressure in inhomogeneous strata lead to pore water concentration in certain local areas, where the soils are compelled to absorb water, causing continuous flow deformation of slopes composed of dilative sand both during and after earthquakes. By studying typical stress paths and volumetric strain component constraints of sand during flow deformation, it is found that the stress-dilatancy under shearing with constant deviator stress along the peak stress ratio and post-earthquake reconsolidation volumetric strain are the two key issues in modeling the post-earthquake flow deformation and failure. The triaxial compression tests under constant deviator stress are performed to observe the relationship between water absorption and shear strain development of sand, and a state-dependent dilatancy model is proposed to predict the large shear strain according to the volume of absorbed water. A description of reconsolidation volumetric strain is also developed based on the consolidation tests on specimens after large shearing. A procedure for modeling the development of the post-earthquake flow deformation is proposed based on the proposed mechanism, mathematical descriptions and simplified finite difference method to simulate pore water seepage.