Experimental analysis of open check dams and protection bars against debris flows and driftwood

摘要

The paper addresses the influence of intense sediment transport (bed load and debris flow) on the efficiency of the structures aimed at the interception of wood logs. In the literature different devices designed to intercept woods are proposed: steel barriers, net barriers, check dam with steel bars positioned in the opening. In this paper we firstly define some fundamental dimensionless parameter governing the phenomenon, in order to determine a rational criterion to evaluate the efficiency of the different kind of devices. In particular, we deepen the interaction between slit check dams and driftwood, in both bed load and debris flow conditions. Starting from the results of this first analysis, we propose some arrangements of steel bars be installed in the check dam. Through a laboratory experimental investigation, by now conduced in simplified conditions (i.e. spherical mono-dispersed sediments), we define some criteria to obtain the best design parameters for the bars, that is their optimal disposition and spacing, in function of the logs characteristics (mainly the lengths). We investigate also the influence of different lengths of the transported woods, finding a general criterion to evaluate an overall length representing the logs ensemble.