Abstract: It is well known that the piping effect has serious hazards to embankments and dams, but the study on the emission of fine particles of soil and on the development of non-uniform penetration of soil foundation after the piping effect is not deep enough. Since the development of piping effect is random and complex, by means of a self-designed equipment, under particular testing conditions, 12 samples with three different pore size distributions are used to make a comparative analysis from the aspects such as piezometric head, flow, coefficient of permeability, trend of fine particles and cumulative amount of sand. Furthermore the coefficient of permeability, void ratio, movement trend of the fine particles in samples and the change law of content of the remaining fine particles are studied. Combined with theoretical calculations, the movement trend of the fine particles in the samples, the non-uniform correlation between the content of the remaining fine particles and the permeability change can be revealed. By using the relationship between permeability and porosity, a theoretical formula can be deduced from the changing amount of accumulated sand over time under the fixed upper head.