Hydro-mechanical analysis of piping erosion based on similarity criterion at micro-level by PFC3D

Internal erosion in river levees and landslide dams has often caused serious damage of the embankment body. As one type of internal erosion, piping erosion is the process in which fine soil particles are detached from the particle skeleton of coarser particles. At microscopic scale, particle composition and migration are the two main issues of piping erosion, which are usually studied by physical model testing and numerical simulation based on continuum mechanics. In this paper, the similarity criteria of internal erosion model testing were firstly derived and then verified by particle flow code (PFC3D). The derived similarity criteria are critical to reproduce the prototype physical model through a numerical model. Secondly, a laboratory test of piping erosion was conducted, and a micro-level particle model based on the similarity criteria was developed to describe the process of piping erosion. This numerical model was developed using the discrete approach-based PFC3D, overcoming the limitations of the commonly used continuum approach. Our laboratory test clearly showed the initiation, development and failure process of piping erosion at microscopic particle level. Our numerical simulations showed very similar trend of these processes as in the laboratory tests, indicating that the PFC3D model (based on the developed similarity criteria) could accurately reproduce the processes of piping erosion. With the similarity criteria developed and strong numerical model capability verified through the laboratory tests, we believe that the discrete approach-based numerical simulation method can be used for piping erosion independently of laboratory tests.