Design Research Of Drain Pipe Net In Three Gorges Reservoir Area Of Chongqing

After Three Gorges Reservoir sluices, water velocity of Yangtse River will slow down, dilution and diffusion ability will decline, too. It is urgent to prevent water pollution and construct municipal wastewater treatment project. As an important part of this, the construction of drainage pipe network system in Three Gorges Reservoir area is taking an important role in promoting economic development, protecting water pollution and safeguarding public health.Majority of cities and towns in Chongqing are so weak in municipal facilities that can't meet the need of water pollution and cure. In addition, the complexity of land form gives the programming and construction of drainage pipelines great difficulties. This study is based on a great deal of domestic and foreign design materials, combines the practical character of Chongqing Three Gorges Reservoir and writer's work experience of many years, analyzes the choice of drainage system, the characteristic and difficult point of pipeline design and gives some suggestions.When choosing the drainage system, there are two situations. One is the alteration of an old town. Separate systems should be used in new zones, and intercepted combined systems are recommended to be used in old zones, because of the geography, the current economic strength, citizen quality and other practical factors. Faulty combined systems should be changed to incomplete separate systems gradually. The other situation is that separate systems should be introduced in a brand new town. When designing, we can use one of the two systems or both of them at the same time according to local characteristics. When designing sewage pipelines, in the purpose of near-remote future combination, appropriate layout, low investment and rapid construction, we should use different lay ways to adapt to different land forms, in terms of the traits of mountainous regions. The paper also discuss how to anticipate sewage rate, how to decide pipe diameter and the depth of burying. Simultaneously, it also discusses the composition of mud accumulation, the relationship between the size of sand grain and velocity and how to decide appropriate minimum velocity.When designing rainwater pipelines, the paper puts forward relative accurate storm intensity formula and give some feasible advice about the decision of runoff coefficient. The layout of pipe culverts and the prevention and treatment of bad land sectors are also discussed. The measures about drainage pipe network design in Chongqing which are discussed in this paper may be consulted in the construction of drainage pipe network in Chongqing Three Gorges Reservoir in the future.