敏感水体公路桥梁桥面径流排水系统设计方法

Runoff drainage system design for highway bridges crossing sensitive water

为减轻公路运输事故中危险化学品产生的径流对敏感水体的影响,并净化桥面降雨径流,探索了跨越敏感水体公路桥梁桥面径流排水系统的设计方法,包含了桥梁纵向排水管槽设计和径流收集池设计2个部分内容。根据城市雨水管道设计原理,结合桥面径流排水特征,提出采用半开放结构的明槽作为排水管槽,并依据暴雨重现期为1年的径流量计算桥梁纵向排水管槽尺寸。基于暴雨强度的概念,探讨初期降雨历时及桥面初期雨水径流量的估算方法,并在此基础上提出了径流收集池池容的设计方法。基于桥面雨水径流细小颗粒物的污染特性和桥面事故径流危险化学品的物理特性,提出径流收集池结构的设计方法。并采用Stokes公式并结合沉淀要求的表面水力负荷,通过实例验证了提出的收集池与传统的事故径流收集池容积对初期雨水危险化学品沉淀的效果。研究结果表明:提出的径流收集池包含初期雨水收集池(池1)和危险化学品事故径流收集池(池2),降雨初期桥面径流先进入池1,初期雨水中细小颗粒物在池1中经过充分沉淀去除;当径流超过初期雨水量时,将超量径流引入池2,池2采用廊道式设计且第3道隔墙底部过水,轻密度危险化学品借助密度差被隔离在前3区上部空间,以达到降雨期间危险化学品事故径流收集而减轻对敏感水体污染的目的。该双池结构不仅可保障初期雨水中细小颗粒物在沉淀池中充分沉淀去除,同时,也可有效收集降雨期间危险化学品事故径流,减轻对地表水体的污染。

In order to prevent water pollution caused by dangerous chemicals leaking accident and initial rainfall runoff,a runoff collection system in highway bridges which go across the sensitive water was designed.There were two parts in this system,one was draining pipe(groove),the other was collecting tank.Based on the principles for urban rainwater draining system designing and runoff characteristics on bridges,a half-opened groove structure and 1 year storm recurrence period were introduced to do hydraulic calculating for longitudinal draining pipes/grooves.According to the concept of storm intensity,a method for estimating the lasting time and the runoff quantity of initial rainfall were discussed.And then the volume of collecting tank was designed in this way.Based on the pollution characteristics of fine particles and the physical characteristics of dangerous chemicals,a construction of collecting tank was introduced.An example was given to illustrate the dangerous chemicals effectively of initial rainfall runoff,which using the traditional collecting tank and the proposed tank.The results show that there are two tanks in the proposed system,No.1 tank is designed for initial rainfall collecting,No.2 tank is designed for dangerous chemicals collecting.Runoff is drained into No.1 tank to let the fine particles to be deposited.The exceeding runoff is drained into No.2 tank,which is designed with galleries,and the water running through the bottom of the third partition wall.The dangerous chemicals which is lighter than water and unmixing with water can be easily collected.The two-pool system would not only make sure the fine particles in the initial rainfall runoff to be deposited,but also effectively collect the dangerous chemicals leaking in a traffic accident at the mean while.It is proved that the design would effectively prevent the sensitive water from being polluted.1 tab,5 figs,25 refs.