the occurring of piping erosion may cause great changes in seepage fields. Numerical simulation to piping erosion developing process is very important to piping erosion prevention and treatment. A method of embedding erosion tunnel in 3-dimensional blocks is put forward to solve series of difficulties in FEM simulation. After discussion of some operating problems
an example of earth dam piping erosion is studied. With numerical calculations
3-dimensional characteristics of dam seepage field under developing process of piping erosion are put into analysis; that shows the concentrative seepage status near the developed erosion tunnel. It is concluded that reforming of seepage field is critical method to prevent piping erosion.