Study Of Characteristics And Design Optimization Of Drainage In Yanan Gully And Valley Area Of Loess Plateau

In recent years, as Western Development carried out, the economic level of Yanan area developed rapidly. However, due to the quite slow construction of drainage pipeline network and wastewater treatment facilities, wastewater was discharged randomly, waters of Yan River was polluted and ecological environment was aggravated continuously. Thus, it is quite urgent to increase the construction of wastewater treatment projects in Yanan area. However, the terrain in Yanan area is complicated, most of its towns belong to gully and valley area of Loess Plateau and the its drainage characteristics differ from that of other plain areas, there are still no similar experiences and guiding standards for the design of drainage pipeline network and a lot of difficulties exist in the planning and construction of wastewater treatment projects. In order to improve and regulate the construction of drainage pipeline network in Yanan gully and valley area of Loess Plateau, comprehensive analysis and study on drainage characteristics and design optimization of Yanan gully and valley area of Loess Plateau was made in this thesis.Based on massive analysis on design materials of drainage pipeline network in western medium and small towns, present situation and existing problems of drainage system in Yanan area, and characteristics of western medium and small towns, selection of drainage system of Yanan area, characteristics and difficulties of design of pipeline network were analyzed, and reasonable suggestion was proposed; according to analysis and comparison on advantages and disadvantages of domestic existing drainage system, technical problems on application of different types of drainage systems in western medium and small towns were studied, and the suggestion of using combined drainage system with interception facility was proposed due to geographical conditions, economy strength and living habits of towns of Yanan area, especially by considering the particularity of gully and valley of Loess Plateau area.Research shows that, when designing sewage drainage system in Yanan area, it is important to consider the geologic and geographic conditions of gully and valley area, and adopt appropriate mode of pipe laying to get low investment and well efficiency. The calculation method of interception ratio of the combined drainage system with interception facility was comprehensively analyzed in this thesis, and the selection of interception ratio for each county was studied by that method. Due to the special terrain feature in Yanan area, adaptability analysis of application of the combined system with interception facility in gully and valley area was conducted in this thesis, and common problems on design of drainage pipeline network in Yanan area were explored in the meanwhile. Based on a case study of design optimization of a drainage pipeline system project in Ansai County of Yanan, it was concluded that, in practical work, the development status and development strategy of the town itself, management level of related industries and natural conditions should be fully integrated; the functionality of city drainage pipeline system should be fully emphasized; the drainage pipeline system should be designed with local characteristics; references and experiences should be provided to those medium and small towns with similar terrain conditions. The result of this study has a guiding significance on the future construction of drainage pipeline network in gully and valley area of Loess Plateau.