Experimental Study on Controlling Debris Flow by a Consecutive Series of Open Type Steel Dams

Abstract

An open type steel dam is a good facility in capturing debris flow for it can prevent the loss of the trapping capacity. In planning for the arrangement of countermeasures in such a basin where has a large amount of sediment discharge, a series of open type dams will be constructed. The arrangement has the following effects; 1)an increase in the reduction rates of peak sediment discharge and total sediment discharge, 2)adecrease in the sediment concentration. In order to confirm these functions, we conducted two cases of experiments-one was using one dam model and another was using two dam models. Three types of dam models (L/d₉₅=3.5(type-1), 2.5 (type-2) and 1.9 (type-3) ) were used, where L represents the distance between steel pipes and d95 represents 95 weight percent grain size. An experimental flume that has a width of 20cm, height of 40cm and length of 500cm, was set at 17 degrees. Water was supplied at 2.0l/sec. Results show that in cases where two dam models were arranged-especially arranged type-2 at downstream, the reduction rates were found to be higher than the cases of using one dam model. Sediment concentrations of the cases of using two dam models were lower than the latter case. In cases of using two dam models of type-2, however, the reduction rates were lower and the sediment concentrations of the case was higher than in the case of using one dam model of type-2.