Study On Special Processes Of Water Intake And Drainage Project On Muddy Coast

In recent years,more traditional thermal power plants and new-type nuclear power plant are needed to match the development of China’s economy.In the construction of power plants,a lot of intake and drainage tunnels are necessary.The tunnels of traditional power plants,especially the drainage tunnels,are mainly designed for coastal areas,therefore,most of the designs adopt a traditional waterfront excavation or a cofferdam excavation method.The favorable locations of power plants becomes few due to the large increase of power plant number,and consequently the geological conditions of drainage tunnel becomes more unfavorable.Therefore,the construction goals can not be directly reached by only using the traditional construction method and technique.At the same time,because of the raised social awareness on the environmental protection,near coastal drainage construction is gradually replaced by far coastal drainage construction.Therefore,the development of new technologies are needed in the far coastal drainage construction.To this end,several case studies were performed on the intake and drainage tunnel of power plants in muddy coastal area in this thesis.The study focuses on the application of the special requirements on the techniques of the intake and drainage tunnel construction in muddy coastal area,by comparing the technique methods,the design of construction management and analyzing the numerical simulations.The main contents and conclusions are as follows:(1)For double steel sheet pile cofferdam construction in high sensitive silty soil,the cofferdam has large deformation and complex loading conditions.Therefore,numerical simulation should be performed before the conduction,and subsequently the parameters and the arrangement of cofferdam should be adjusted.The nonuniform stiffness of double steel sheet pile is one of the main reasons for the incompatibility of deformation when the span is large.However,it is economically better than the traditional rock cofferdam.In the future,the feasibility of double steel sheet pile in muddy soil can be improved by improving the design on the integration.(2)For muddy coast offshore drainage culvert,the economical efficiency of using a land and water combined method is much higher than that of dry cofferdam excavation.Additionally,the combined method can avoid leakage and destabilization due to the large deformation of cofferdam.The producing,transporting and installing of water culvert needs a further improvement based on the traditional technique.Especially,the rough operations in water,the low guarantee on the quality accuracy and other problems need further improvement.Small pit dry mode operation can be used in the construction of junction between land culvert and water culvert,considering the pit has a small volume and the cast-in-place structure can satisfy the requirements on the deformation compatibility and sealing.The combined construction method with considering the location properties will be one of the construction method goals in the future.(3)For intake and drainage construction in high sensitive muddy soil using shield method,the equipment should be properly arranged and improved by taking into account of the engineering geology conditions and the requirements on environmental protection.However,the deformation and settlement of foundation during and after construction may not be controlled by adjusting the shield machine.The proposed stage-construction method can significantly decrease the impact of construction on the sensitive ground environment.In addition,the comprehensive adoption of monitor and countermeasures is necessary to decrease the impact.In summary,the focus of the thesis is on the technique of intake and drainage construction in various engineering structures and various geological environments in muddy coastal area.The conclusions were drawn based on the comparison of designs,the numerical simulations and the construction practices.The research results offers an alternative idea for solving the technique problem of intake and drainage construction in muddy coastal area.