Collapsing process of uniform granular slopes

The processes of rock avalanches and slope sliding are closely related to the granular physics. In this study, the relaxation process of dry granular slopes is experimentally examined in a transparent plexiglass chute with particle image analysis. Three types of uniform spherical beads were used at different bottom slopes and channel widths to explore these flow characteristics. The angles during the early slip phase are close to the failure angles associated with active earth pressure according to the Mohr-Coulomb friction law. For given sizes (d) and slopes (theta), the flowing progress can be represented by a logarithm curve, being decreasing with the dimensionless time parameter t*. Velocity profiles measured at the side-wall depict a linear distribution on the top and an exponential tail near the static region at the bottom. According to the conservation of mass and momentum, the measured depth-averaged velocity and flowing thickness collapse well with an exponential laws.