Experimental Study of a Grid Dam with Narrow Pipe Interval of Upper Grids

Abstract

When installing grid dams to trap debris flow, it is important to select the interval of steel pipes of the grids with consideration for characteristics of debris flow such as grain size, sediment concentration, and so on. Since the front of debris flow contains coarse grains, the sediment concentration there increase most, while the other sections of debris flow that follow the front contains fine grains, their sediment concentration decreases. The grids for trapping debris flow have such an effect that the front of debris flow is trapped by the lower grids while the following debris flow is trapped by the upper grids. However, since the interval of steel pipes of both the upper and lower grids are conventionally made the same, we thought it might be better to narrow the existing steel pipe interval of the upper grids.
To this end, we carried out flume experiments using grid dam models to examine whether or not the upper grids having a narrow pipe interval is more capable of trapping debris flow. As a result of the experiments, we found that the grid dam models designed to have narrow pipe intervals of the upper grids are capable of trapping more volume of sediment transported by debris flow.