Overflow Cofferdam And Diversion Scheme Study For Qingjiang Shuibuya Hydropower Project

Overflow cofferdam is a very effective diversion method in construction of hydraulic project. It is economic and applies to mountain and valley river. Using overflow cofferdam can reduce the volume of cofferdam and duration of building it.This thesis systematically studies some important subjects in theoretical and applicable aspects, on which the overflow cofferdam needs to solve at present during key water control project construction, such as diversion ways and the type of overflow cofferdam, diversion standard, and the bedding course of the downstream protection slop of concrete slab on overflow cofferdam. Moreover, according to the experiment of hydraulic construction model, the thesis studies the overflow cofferdam and diversion scheme for Qingjiang Shuibuya Hydropower Project. It consists of 5 chapters.Chapter 1 introducts the course of selecting topic, the present situation of the study on this thesis subjects and the main content on this thesis. Chapter 2 systematically analyses some important factors which affect the choice of construction diversion ways and the type of overflow earth-rockfill cofferdam. The diversion standard of overflow cofferdam is divided into inflow standard, waiter-retaining standard and overflow standard, and the determination method on the three diversion standards is put forward. In chapter 3, by means of the experiment of hydraulic construction model, the relations for Shuibuya Hydropower Project as following is been studied. As to the different elevation of upstream overflow earth-rockfill cofferdam and downstream RCC cofferdam, the rate of flow between cofferdam and dam, flow speed, flow pattern. Based on this, it optimizes the model and the elevation of upstream and downstream cofferdam. It studies the design of the bedding course of the downstream concrete slab protection slop of overflow cofferdam. It puts forward relevant risk rate's calculation models, and gives the risk rate's calculation methods. Chapter 4 synthetically considers the key-points and difficulties of Shuibuya Hydropower diversion. It carries out diversion scheme suitable for Shuibuya high concrete facing rockfill dam.In a Word, based on the diversion schemes of overflow cofferdam of the Qingjiang Shuibuya Hydropower Project, the structure of cofferdam, the stability of overflowing status and the protection methods have been researched. Those analysis models andprotection methods are applied in the practices of above project, and the validities of analysis models and protection methods are proved.