In order to show the meso-mechanical of piping in sandy soils, the dynamic process of piping caused by the transportation of fine particles in the soil is studied by sand launder model test of piping and numerical simulation of PFC. Based on the results of the numerical simulation, the rules of the sample’s meso movement and the liquid’s movement are studied and are compared with the results of sand launder model test. The result indicates that the critical hydraulic gradient derived by numerical simulation is nearly equal to that derived by sand launder model test in different cases of particle,porosity and permeate diameter. Therefore, researching the piping by PFC is reasonable and a new approach to explain and analyze piping in meso.
