Model Tests of Reinforced Revetments for Debris-Flow Control

In this study, a small-scale model test was conducted to simulate the impact of debris flow on reinforced-soil structures. Materials were selected according to similitude laws to simulate the particle size distribution of the material at a debris flow site (Fengchu) and the geosynthetics. During the test, the movement of the materials was recorded by three video cameras. The analyses of the front velocity and mean velocity for specific particles were performed by particle image velocimetry (PIV) and particle tracking velocimetry (PTV). Moreover, a device was set up at the toe of the slope for measuring the impact force from debris flow. The variations in velocity and impact force were studied in terms of different quantity of flow. The mechanic behavior of the barriers (revetments) and comparison between two types of barriers were discussed. In the debris flow simulation test, flows of different quantities were considered. According to the physical test result, the variation in front velocity was not obvious. However, the quantity of flow had influence on the mean velocity. Although the initial mean velocity of large quality flow was slower, the mean velocities of flows with different quantities were almost the same. Regarding for the impact force, the quantity of flow had little influence on the pattern of time history. As the quantity of flow was increased, the maximum impact force increased as well; nevertheless, the impact force per unit area was not increased proportionally to the impact force. It was found that the impact force at the middle was larger than that at the side of the flow. To measure the impact of debris flow on reinforced-soil structures, two types of barrier, wrap-around and glued facings, were taken into consideration. Based on the observation, the glued-facing barrier depressed more at the up-stream side and bulged more at the downstream side than the wrap-around barrier. After uncovering the embedded layer, the foundation of wrap-around barrier had significant lateral deformation at the downside; while the glued-facing barrier had small overall sideway movement. Both barriers did not have rupture of reinforcement or soil washed out, indicating the good function of the GRS barriers.