The particle flow code（PFC） was adopted to simulate the cyclic shear test of saturated sand under undrained condition.The influence of different conditions of sand samples on liquefactions was studied. The meso-mechanism of the large limited post-liquefaction deformation was explained by pore distributions. A statistic code was developed to quantify the arrangement of particle and pore

and standard deviation of porosity was proposed to measure the post-liquefaction volume shrinkage potential. Then relationship between the standard deviation of porosity and the limited large post-liquefaction deformation was investigated. It was found that initial conditions have little effect on the ultimate state of post-liquefaction sample

while it only influences the cycle numbers of initial liquefaction. The large limited post-liquefaction deformation on saturated sand in laboratory test repetitively occurs during numerical simulations. The homogenization of pore and the increasement of distance between particles caused by the accumulation of sand volume shrinkage potential was the meso-mechanism of the generation of the large limited post-liquefaction deformation during cyclic shear. As a quantitative index of pore homogenization

standard deviation of porosity got a favorable correlation with the shear strain amplitude in each cycle.