Soils moving is one of the geotechnical problems

which can be described as a granular flow induced by inclined plane. This work aims to investigate the drag and lift forces acting on the inclined intruder. By using the inertial number concept to confirm the flow regime

a parameter named dynamic friction coefficient is induced to this non-quasi-static flow.  By improving the Coulomb model

the displacement field is obtained by two dimensional discrete element method

and the wedge model for drag and lift forces is built. The results show that  drag force is dependent of the inclined angle when the other conditions are the same

but the lift force is decreasing with the inclined angle. Drag and lift forces are the horizontal and vertical components of the total force

respectively. And the ratio of drag and lift forces is just equal to the tangent value of the inclined angle. The dynamic friction angle is the quadratic function of velocity and inclined angle. This model can predict different case in different inclined angle and velocity.