Abstract: It is difficult for engineers to numerically simulate the piping process. The conventional finite element method is inappropriate and not theoretically rigorous, while the discrete element method is time consuming and not suitable for practical application. By using the hydraulic theory for pipe flow and conventional seepage theory in the rest, the seepage-pipe flow coupled method can appropriately simulate the advancing pattern of the piping at smaller computational cost. Based on the coupled method and the introduction of particle size distribution, an approach to simulate the piping channel development over time is proposed. Simulation of piping in foundation with a cut-off wall shows that the progression rate is rather slow at the beginning and acceleratingly increases when the piping channel reaches the bottom level of the cut-off wall. The investigation implies that the cut-off wall changes the direction of piping channel progression and reduces the pace of development, which may be beneficial to treating dangerous situations.