| dc.description.abstract | As global climate change intensifies and human activities increase, the frequency and severity of natural disasters have risen accordingly, with landslides, debris flows, avalanches, and earthquake-induced slope failures being particularly significant. These events pose direct threats to human safety and have profound effects on ecosystems and long-term geomorphological transformations. Consequently, this study focuses on observing the flow behavior of granular collapses through experimental methods.
This research aims to explore the behavior of high-speed granular flows impacting obstacles. Experiments were conducted using a closed inclined chute to investigate the effects of different granular materials (glass sand and quartz sand) and various barrier materials (PVC, EPE, and LDPE) at different inclination angles on the flow behavior and impact forces of the granular streams. Particle Image Velocimetry (PIV) was utilized to measure the velocity changes in the flow field, and load cell were employed to assess stress variations. Throughout the experiments, the inclination of the chute was adjusted, and detailed records of the flow behavior and stress distribution for each set of experiments were maintained.
The experimental results indicate that the material properties of the granules significantly influence the dynamics of the granular flow, primarily manifesting as vertical jetting or accumulation modes. As the inclination angle increases, both the maximum flow velocity and the impact velocity also increase, yet they decrease along with the flow length, with the impact velocity generally being lower than the maximum velocity. For glass sand, the shock wave velocity decreases with the flow length at smaller inclination angles; at larger inclination angles, the shock wave velocity initially decreases sharply and then stabilizes. For quartz sand, at lower inclination angles, the shock wave velocity remains within a fixed range due to its angle of repose being greater than the inclination angle, resulting in unique flow behavior. Regarding the impact forces, they increase with the inclination angle, and altering the material of the obstacle can effectively reduce these forces, with the distribution of impact forces showing nonlinear variations, categorized into five distinct types. Additionally, theoretical models were employed to predict the maximum run-up height and the overall impact force, with comparisons to experimental data revealing that when the density ratio is 1, the predictions accurately reflect the maximum run-up height. For glass sand, the predicted maximum total impact force generally has an error margin within ±10%. Finally, to quantify the differences, the deposition angle was calculated and found to increase with the inclination angle, with the corresponding Froude number also increasing accordingly. | en_US |