Abstract: Based on the basic internal erosion control equation and the soil mechanical constitutive model, a coupled internal erosion and mechanics model is proposed in this paper. The model can reflect the dynamic changes of the soil physical and mechanical properties such as the fine grain particle content, the porosity and the pore water pressure during the internal erosion. The model is simulated by finite element method to reveal the mechanism of internal erosion, describe the characteristics of internal erosion in the process of occurrence, development and stability, and explore the change law of physical and mechanical properties in the process of sand internal erosion. The erosion process can be divided into three stages: the initial erosion stage, the erosion process just began to develop slowly; the steady erosion stage and the erosion rapid development stage; In the erosion equilibrium stage, the sedimentation rate and the loss rate of fine grain particles gradually reached the same, and finally the erosion stopped. The internal erosion changes the physical and mechanical properties of the soil and redistributes the soil pressure, which leads to the surface settlement. The magnitude of settlement is positively correlated with the degree of erosion, and it has a great influence over the drain hole.

Key words: Internal Erosion, Finite Element Method, Three-phase coupling, internal erosion mechanism