Experience from around the world has shown that net barriers are ideal for arresting steep creek hazards such as debris flows. Net barriers can regulate the peak discharge by allowing some sediments to pass. Existing studies that focus on the impact dynamics of barriers mainly focus on the impervious barrier, such as concrete barrier and check dam. The current design approaches regard the barrier as impervious without considering the sediments passing caused by mesh opening. The principal objectives of this research are to reveal the effects of mesh opening on the interaction between debris flow and net barrier.

The hydrodynamic equation based on conservation of momentum is combined with the Berverloo law to derive the new impact equation explicitly consider the effects of the mesh siz...[ Read more ]

Experience from around the world has shown that net barriers are ideal for arresting steep creek hazards such as debris flows. Net barriers can regulate the peak discharge by allowing some sediments to pass. Existing studies that focus on the impact dynamics of barriers mainly focus on the impervious barrier, such as concrete barrier and check dam. The current design approaches regard the barrier as impervious without considering the sediments passing caused by mesh opening. The principal objectives of this research are to reveal the effects of mesh opening on the interaction between debris flow and net barrier.

The hydrodynamic equation based on conservation of momentum is combined with the Berverloo law to derive the new impact equation explicitly consider the effects of the mesh size. The new impact equation demonstrates the impact force decreases with mesh size increasing (S/δ), which show the potential to optimize the design of the net barrier and multiple net barriers. Moreover, physical and numerical modelling are adopted for this study. A five-meter flume model is used to investigate the effects of mesh size on the impact mechanism of granular flow on the net barrier. The mesh size (S/δ) in a range of 1.0 to 7.7 is examined in the series of test. The effects of mesh size on the impact kinematics are analyzed using Particle Image Velocimetry (PIV), The impact force of granular flow and retained volume of granular particle on the net barrier are discussed. Then the physical experiment in the five-meter flume is used to calibrate the numerical model using a three-dimensional discrete element method (DEM) to conduct a back-analysis. To ascertain the effects of mesh size on energy change of granular particles assemblies, three different mesh sizes are simulated in the numerical model. The energy change for different mesh size (S/δ) is investigated. The newly-developed twenty-eight-meter flume is then used to simulate the debris flow composed by natural debris material. Three large-scale flume tests are conducted with different mesh size (s) to evaluate the performance of the new impact equation. The effects of mesh size on the debris flow impacting on multiple net barriers are investigated. The velocity attenuation of two net barriers is investigated. The distribution of impact load and retention volume affected by the mesh size are studied.

The impact mechanism of granular flow on the net barrier is revealed in this study. The formation of the dead zone by a net barrier is determined by the ratio of mesh size and particle size (S/δ). A fine mesh size ratio (S/δ=1.0) leads to an increasing dead zone. Whereas, a larger (S/δ=2.3) mesh size ration results in a dead zone first increasing and then decreasing. The proposed new impact equation explicitly considering effects of mesh size has shown to be conservative for single-size dry granular flows on net barriers (0

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