城市道路横截沟泄流效率试验研究

Experimental study on the hydraulic efficiency of continuous transverse grates

横截沟常设置于停车场入口、城市下穿隧道、机场停机坪等无适宜横坡或纵坡坡度过大的场所对道路径流进行截流,其泄流效率决定了降雨期间地下管网系统的泄流量,提高横截沟泄流效率对预防城市内涝的发生具有重要意义。利用长12 m、宽3 m、高0.5 m的试验平台,研究了在不同的入流径流量和纵坡坡度组合下8种横截沟雨水篦子对径流的截流情况,重点分析了上游水流水力参数及横截沟雨水篦子几何参数对泄流效率的影响。试验结果表明:不同篦子泄流效率与径流弗劳德数间的关系不一致;增大篦子开孔长度对提高泄流效率比增大开孔面积更有效;在篦子面积、开孔率、开孔面积相同时,开孔交错分布的圆形开孔篦子比开孔对称分布的矩形开孔篦子更有利于泄流。在曼宁公式及孔口出流公式的基础上提出了计算试验篦子泄流效率的经验公式,预测值与试验值之间的相对误差小于15%。

Continuous transverse grates are commonly used in some urban or impervious areas to collect the runoff(the entrance of parking lots,under-crossing tunnels,and airport aprons),where it is hard to place conventional inlets due to lack of suitable transverse slopes or steep longitudinal slopes.Hydraulic efficiency of continuous transverse grates determines the flow rate into the underground sewer system during rainfall and is of great significance to preventing the occurrence of urban waterlogging.Eight types of continuous transverse grates commonly used in China were experimentally tested in this study with different approach flows(Q=10~80 m3/h)and a set of longitudinal slopes(SL=1%~4%).A full-scale physical model simulating a 12 m long,3 m wide road was constructed in the hydraulic lab in Hefei University of Technology for the hydraulic tests.Hydraulic efficiencies of these grates under different conditions were calculated during the tests,and their influencing factors were analyzed,including hydraulic parameters of the approaching flow(Froude number)and the geometric parameters of the grates(total area,length of the opening in flow direction,opening style and opening rate).The experimental results show that the hydraulic efficiency of different continuous transverse grates may not have a consistent relationship with the Froude number.The length of opening in flow direction may have greater influences on the efficiency than the opening area or rate.Compared to grates with rectangular openings symmetrically arranged,when the opening area and rate are the same,the grates with circular openings staggerly arranged are found to perform better for capturing runoff.Based on the Manning Equation and the orifice outflow formula,a set of empirical equations were also presented to relate the hydraulic efficiency and influencing factors.Good agreements were obtained between the predicted and measured results with relative difference of less than 15%.