Abstract: The impact mechanical model changes of granular flow caused by the changes in slope angle and rigid wall slope are neglected problem presently. The discrete element method (DEM) is utilized to investigate the influences of slope angles on the impact properties of dry granular flow impacting on the rigid wall, which is based on the laboratory experiment of granular flow impacting on low-angle retaining wall. Two impact mechanical models are proposed according to the accumulation characteristics of dead zone, the impact characteristics of flowing layer and their interaction characteristics. The results show that the slope and the angle of the retaining wall change the accumulation characteristics of the dead zone and change the impact direction and impact force of the flowing layer. The maximum normal impact resultant force (NIRF) can be estimated by the formula of static earth pressure when the slope is less than 40 degrees, since the flow layer impact the retaining wall indirectly at the moment of maximum impact force. With the increasing of slope, the kinetic energy of the flowing layer increases. At the moment of the maximum normal impact force, the flowing layer impacts the retaining wall directly. However, the dead zone has the buffer and deceleration effects on the flowing layer. This leads to decrease of direct impact force on the retaining wall. The load of dead zone on retaining wall mainly includes the direct impact force of the flowing layer on the dead zone along the slope, the shear friction force of the flowing layer on the dead zone and the static earth pressure of dead zone. The ratio of impact force of the dead zone on the retaining wall increases to 90% of the maximum NIRF. When the slope angles increase from 40 to 50 degrees, the ratio of shear friction force increases from 15% to 49% of the maximum NIRF. The friction coefficient between dead zone and flowing layer also changes from rolling friction coefficient to static friction coefficient. The shear friction force by the flowing layer onto the dead zone provides a new research idea for the estimating model of granular flow impacting on rigid retaining wall.

Key words: granular flow, rigid barrier, discrete element method, impact, friction