| With the persistent steady high-speed development of economy in China, more and more hydraulic and hydropower projects will be constructed in order to meet requirements of economy development by exploiting water energy resources. In China, water energy resources in rivers' middle and up stream area with less population and undeveloped economy is much more than rivers' downstream area with hill and plain, more population, developed industry and urgent needs for water energy. In recent years, because of high-speed and over-conventional development of economy in rivers' downstream area and urgent needs for exploitation of local water energy resources, we have to review and restudy those viewpoints which have been deemed unfeasibility for using normal development method or unfeasibility for economy or more difficulty in technique and find out a over-conventional method for exploitation of water energy resources in rivers' downstream area and meeting requirements of local economy development.According to actual conditions of geographic environment of Shawan river section on downstream of Dadu river, in this paper, we adopt a over-conventional composite development program of river channel type powerhouse with long tailrace, which is available to develop the water energy on Shawan river section. The tailrace of Shawan power station has new functions of concentrating generation head and increasing installation capacity, which can change traditional development method (powerhouse followed by long tailrace in development methods of diversion type, river channel type and dam toe type) into a new composite development method. This new method is a supplement and an improvement to traditional method.The tailrace of Shawan power Station has available water head of 14.5m, design discharge of 2203.2m3/s, available installation capacity of 220MW, length of 9.0km and total cost of 542.00 million yuan RMB. Each index mentioned above is more than that of similar project in Sichuan province and the composite index consisting of design discharge, available installation capacity and total length make this tailrace become the biggest one in China.Because of long tailrace, more design discharge and involving in issues related to flood control, spoil, environment protection, water and soil conservation, safety during operation and sedimentation etc., Shawan power station has become the focus which was reviewed, consulted, evaluated and disputed. Many experts in China deem that the tailrace plays an important role for this project and there is not similar project in China, which can concentrate a half of water head and obtain so much more installation capacity. Furthermore, if issues involved can be solved appropriately, as a result, economic benefits will be very remarkable and experiences obtained from this project will have evaluation of application and dissemination under suitable conditions.In accordance with characteristics of long tailrace of Shawan power station, in this paper, we analysis those critical technical problems caused by long tailrace, such as development program, general layout of project, flood release and energy dissipation under gates, water flow in river section of tailrace and inside tailrace as well as characteristics of sedimentation. After verifying by mathematical model and hydraulic model test, the result is that water energy of Shawan river section should be developed by using a new composite development method which is river channel powerhouse with long tailrace. This new development method has been affirmed and accepted by experts from China Water Resources and Hydropower Engineering Consulting Corporation and China International Engineering Consulting Corporation and it has been approved to be the program for design and implementation. |
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