The evolution of piping is a complex process, which is influenced by many factors. In order to investigate the influence of flow condition and soil particle composition on the piping process, a list of experiments on two typical types of non-uniform flow and three kinds of soil particle composition was carried out using the self-designed apparatus. The results indicated that divergent flow reduced the discharge in the outlet, meanwhile the critical hydraulic gradient for piping was large and the erosion rate was slow. The hydraulic gradient in the soil sample gradually decreased along the divergent flow direction before the erosion. On the other hand, the convergent flow made the discharge in the outlet large, the critical hydraulic gradient small, and the erosion rate fast. The hydraulic gradient in the soil sample gradually increased along the convergent flow direction before the erosion. Furthermore, the coarser the fine particles, the larger is the critical hydraulic gradient and the slower is the developing speed of the piping channel.
