Experimental Study On The Hydraulic Efficiency Of Street Inlets

In recent years,waterlogging disasters have occurred frequently in many Chinese cities,causing a great amount of economic losses.To improve the efficiency of the existing municipal drainage facilities is a cost-effective way to alleviate urban waterlogging and is worth of further studies.Street inlets serve as the entrance of the surface runoff into the underground drainage pipeline,and their discharge efficiency determines the drainage capacity of the municipal drainage system.In this study,a 1:1full-scale physical model(12 m long,3 m wide and 0.5m high)was built to investigate major factors that influence the hydraulic efficiency of street inlets,including street slops(1%～1.5%cross slopes,0.3%～5%longitudinal slope),approaching flow rate(0～70 m~3/h)and inlet types(two types of gully inlet,one curb inlet and one combination inlet).And a total of 277 experiments were carried out under different working conditions.Through the analysis of the experimental phenomena and the measured experimental data,the variation curves of the width and the depth of the approaching flow along the road were plotted.The captured flow and the hydraulic efficiency of different types of inlets were analyzed and compared.Based on obtained data,the relationships between inlets efficiency and influencing factors were fitted by using regression analysis.Presented models were compared with previous empirical formulas.Research results show that the inlet type has significant influences on the flow width,depth as well as the hydraulic efficiency.Only when the flow rate(≤10 m~3/h)was very small,all the runoff can be totally captured by the inlet;With the increase of the road runoff,the hydraulic efficiency shows a nonlinear downward trend.The longitudinal slope generally has little influence on the discharge efficiency,but can significantly increase the efficiency of the curb inlet.The increase of the cross slope can enhance the discharge efficiency of all inlets.Presented empirical formula were used to deduce the optimal spacing of the street inlets.