The Study On Pipe Network Model Of Urban Rainwater Drainage System

The urban rainwater drainage system is one of the important infrastructure in city, and the degree of perfection in rainwater system determines the level of the normal operation of urban production and living. According to the configuration of urban rainwater drainage system, the rainwater drainage system can be divided into two levels. One is urban rainwater pipe network, the other is flood-relief river. The two kinds of rainwater system is connected to each other and interact. The change of water level and flow in flood-relief river directly affect the operation of rainwater pipe network. Therefore, we must be couple the two kinds of drainage system, to establish a coupling model of urban rainwater drainage system. Through it, we can comprehensively and systematically analyze the actual operating conditions of urban rainwater pipe network and recognize the area where may appear the waterlogging, thereby pertinently transform and assess the rain pipe network. The study conducted a certain attempts, and carried out the following main work:1) From the perspective of urban rainwater drainage system, we analyze the links between the urban rainwater pipe network and flood-relief river, and discuss the theoretical basis for the coupled analysis of two-stage drainage system; from the perspective of rainwater runoff and the process of rainwater drainage, we study the mechanism of waterlogging, and analyze the related waterlogging prevention measures.2) Through analyzing the process of rainwater runoff, we use mean of mathematic modeling the established a coupling model of urban rainwater drainage system including input model, hydrodynamic model and coupled model and study its feasibility and applicability. Analysis shows, the CHM can be used for rainfall model to simulate rainfall; the Horton model can be used for runoff producing model to simulate the infiltration; the isochronal streamline method can be used for concentration model to simulate flow concentration. Its modeling and calculation tools can be used the rainfall runoff module of MIKE URBAN. The dynamic wave can be used for storm sewer network hydrodynamic model to simulate flow concentration in network. Its modeling and calculation tools can be used MOUSE module of MIKE URBAN. The four-point implicit finite difference theory can be used for river network hydrodynamic model to simulate flow concentration in network. Its modeling and calculation tools can be used HD module of MIKE 11. In accordance with pipe network model theory, we use MIKE FLOOD as model coupling and calculation tools to the hydrodynamic exchange process between urban rainwater pipe network and river network.3) In an area of Chengdu as an example, we established a simplified model of urban rainwater drainage system in the region. According to the relevant provisions of outdoor drainage design specification, we use the return period of 3 years non-constant rainfall scenarios as input conditions. To simplify the calculation of model and improve the efficiency and accuracy of the calculation results, when the model calculating, the network system is divided into two levels based on the diameter size of the rainwater pipe network. We will calculate hierarchically. By the hydrodynamic coupling calculation of the first level of rainwater pipe network and river network, we can get the water level and flow conditions change with time of the junction between two levels of the rainwater pipe network. Its time series can be substituted into the second level of rainwater pipe network system model as a boundary condition, and we can accurately calculate the flow rate and water level changes of each node. For the area where may appear the waterlogging, we use the recessed green space and detention tank to reduce the peak flow of the drainage system, and this simulation analysis showed that these measures are effective.The research achievements provide a new approach for analysis of urban rainwater drainage system and urban waterlogging prevention system, and it has some practical reference value.