| dc.description.abstract | The disasters like debris flows, flooding and avalanches have caused many deaths and injuries on the earth, and it is important to understand the inner behavior of debris flows. In this thesis, we will investigate the collapse of rectangular granular piles in the narrow channel for both dry and wet conditions, and validate the DEM simulation with the corresponding experimental results in wet condition. The effects of different aspect ratios and particle diameters on the behavior of granular flows during collapse are also analyzed. We use the Voronoi imaging method to measure the velocity of granular flow.
Some characteristics such as distribution of velocity, velocity profile, thickness of flowing layer and flow rate at the outlet are analyzed in this thesis. Results show that greater velocity on the flowing layer occurs in the high aspect ratio. Likewise, larger particle tend to have greater velocity on the flowing layer during collapse. The flow rate and flowing layer at the outlet reach a maximum initially and decline with time. As the aspect ratio increases, the greater flow rate occurs at the initial period, and declines sharply with time. In the comparison of different particle diameters, the flow rate declines more slowly for large particles than for small particles. By comparison with experimental data, the simulation results show greater flow rate at the outlet and the great velocity in the free surface at initial collapse. However, both results between experiment and simulation show good agreement at later period. The pressure dip is obvious in the formation of the granular pile at initial collapse. | en_US |