Laboratory Study of Blockage at the Entrance of Box Culverts under Unsteady Flow Conditions

Culverts are important structure to convey water under roads and rail roads. Blockage or clogging of drainage channels by woody debris is one of the serious problems in the design and operation of road culverts that has not been studied well. In this laboratory study, the entrance blockage of a box culvert model due to the accumulation of woody floating objects is investigated. Also, the influence of hydraulic and geometric parameters such as flow velocity, elapsed timeand the entrance flow depth in the culvert were studied. Laboratory observations showed that the entrance blockage increases as the interval time between the arrivals of woody floating objects reduces. The maximum blockage occurred in the falling limb of the hydrograph and the last time step. Using the experimental results and dimensional analysis, some dimensionless parameters are reported and their variations against the culvert entrance blockage are evaluated. The most effective parameters are identified using statistical analysis with SPSS software. Finally, a non-dimensional linear relationship is derived to determine the percentage of blockage as a function of the effective parameters.