格子型ダムのピーク流砂量減少率に関する研究

抄録

One of the most general used method of counteracting debris flow using structures is to catch all the sediment transported by the debris flow. It has been pointed out that current the closed-type dams lose this ability to catch debris flow actually occurs due to a gradual decrease in the dam's sediment trap capacity. Open-type dams have been designed and constructed to let the unharmed sediment passing through freely while catching the harmful sediment downstream.
It has been commonly reported that the ability to catch sediment with a grid is influenced by the ratio of the minimum grid distance (L_min) to the maximum grain diameter (d_max). This parameter, however, dose not sufficiently explain the ability of the grid to catch the head of the debris flow. The concentration of sediment (C) and the flow velocity could also act as parameters for this purpose. In this report, grid-type dam models having a wide variety of grid distances are experimented with at different flume slopes; 10 degree, 15 degree and 20 degree. The experimental results are then analyzed using the previously mentioned three parameters. Since flow velocity does not influence the rate of reduction of peak sediment discharge (P), an experimental equation is deduced as follows:
P=1-0. 11·(L_min/d_max-1)^0.36·C^-0.93
This equation makes it possible to predict the effectiveness of controlling transported sediment with open-type dams on bed slopes where debris flow and flash floods occurr.