Physical Modeling Study on Hydraulic Performance of Rectangular Deck Drains

摘要

An innovative rectangular deck drain has been developed by the Texas Department of Transportation (TxDOT) Bridge Division. It fits between the deck reinforcement, does not interfere with the structural connection of the rail to the deck, and is available in two widths. An equation for slotted drains developed by Federal Highway Administration (FHWA) was adopted to model its hydraulic performance; however, the model neglects the difference between the two drain widths. To better understand and model the hydraulic performance of rectangular deck drains, a physical model was built and an extensive experimental study was performed by varying drain sizes, number of drains in series, approach discharges, cross slopes and longitudinal slopes. Measurements included a series of water depth (y) and ponding width (T) at different locations, the captured discharges and bypass discharges. Applying the adopted slotted drain model to the experimental data predicts more conservative drain length than the drain length in the experiments. An accurate prediction model has been developed based on the weir equation. The model demonstrated the capture discharge is related to the drain size (L+W), the number of the drains (N), the Manning's coefficient (n), the water depth of approached gutter flow (y), the longitudinal slope (S_o), and the cross slope (S_x). Rating curve for each individual drain is the same when the drain size is 4 by 8 inches; however, it is decreased slightly along the flow direction when the drain size is 6 by 8 inches.