Item: Energy dissipation studies on model control structures using an avalanche chute
Title: Energy dissipation studies on model control structures using an avalanche chute
Proceedings: Proceedings of the 2006 International Snow Science Workshop, Telluride, Colorado
Authors: Ansar Hamid Sheikh, Satish Chandra Verma, Amod Kumar Snow and Avalanche Study Establishment, Research & Development Centre, Himparisar, Chandigarh- 160036
Abstract: Design of avalanche control structures in middle and runout zones of an avalanche requires a careful study of the flow-structure and its interaction with the defence mechanisms. To investigate the interaction of the flowing snow mass with the obstacles (friction blocks) of different geometries, a series of experiments were conducted in a 61m long snow chute. The flows generated are approximated as avalanche-like flows as they show typical features such as a steady velocity along the track, longitudinal spreading and almost fluidized flowing characteristics despite the smooth chute surface. The intelligent design of the upper chute part, which widens immediately after the release of snow mass allows lateral spreading and this step ensures this highly desirable flow behavior generally observed in the natural avalanches. In this study, we report a series of experiments on model control structures in the form of mounds, a blunt body of similar projection area which are of a comparable height to the flow depth and a catch dam. The retarding effects were investigated by a direct measurement of the velocity of flow at various sections using CCD Cameras, its run -out length and location of center of mass of the final debris deposited. The experimental results can be helpful in predicting the behavior of flow around the obstacles. The experiments show that the avalanche currents generated in the snow chute detach from the top of the obstacles in the form of a jet and a granular jump is created, which results in a sufficient dissipation of the energy and a possibility of a shock wave traveling in the upstream direction. The effect of several arrangements in the layout of the mounds on their retarding effects was examined. It was observed that mounds with height more than two times the flow depth, can lead to a significant reduction in the runout length. However, at low flow depths the effectiveness of the blunt body is more because the avalanching snow splits into different segments and the flow profile is very close to the bed slope. On the contrary, when the flow depth is of the same order of magnitude as the obstacle height, the mound becomes more effective as the flow detaches from the top of the blunt body and travels a much larger distance at high velocity, while as in case of mounds jet is formed both in horizontal and vertical directions, and travels a comparatively less distance. The study of the jet traverse in the vertical direction becomes very useful in determining the effective distance between rows of retarding barriers.
Keywords: avalanche-like flows, dynamic similarity, froude number, large, scale snow experiments, energy dissipation ratio
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