Abstract: In the area of sandy and silty soil, seepage is the main factor that threatens the safety of foundation pit and surrounding environment. The complex system of foundation pit is composed by soil、water and surroundings, and the factors of seepage failure are complicated. Based on the former analysis of seepage failure of soil, a method for analyzing foundation pit seepage failure model is proposed; the method can considers the influences of seepage, excavation and the deformation of surroundings. The foundation pit seepage failure model in homogeneous soil is gained by this method. According to the finite element numerical simulation results of a practical project, the process of seepage failure is gained. The conclusions of those results show that not only the checking computations of flowing sand and piping should be made, but also the unitary failure of foundation pit system should be considered.

Key words: seepage, seepage failure, critical hydraulic gradient, stress path test