Research on the Slip Surface and Active Earth Pressure of Cohesionless Soil Based on Discrete Element Method

This study employs Particle Flow Code (PFC) to investigate the effects of wall-soil friction angle (δ), internal friction angle (φ), and retaining wall inclination angle (ε) on the slip surface morphology and active earth pressure of cohesionless soil, with emphasis on soil arching effects. Key findings include: (1) As δ increases, the slip surface transitions from a π/4 + φ/2-inclined plane to an "S"-shaped curve; as ε decreases, it shifts from a plane to a "J"-shaped curve, with the slip surface bottom intersecting the movable wall heel. (2) The retaining wall’s lateral stress stabilizes when translation reaches 0.4% of soil height (H), indicating active failure. (3) Soil arching-induced stress deflection is asymmetric between the wall and slip surface, with more significant deflection near the wall. (4) Maximum active earth pressure is negatively correlated with φ, positively correlated with ε, and weakly influenced by δ. Compared to the π/4 + φ/2 planar slip surface, the PFC-simulated slip surface causes up to 12.5% and 13.1% differences in resultant force and bending moment, respectively. This research provides a reference for accurate active earth pressure calculation in cohesionless soils.