| With the rapid development of social economy and mushrooming energy demand, clean and green energy has become essential to the sustainable development. Nuclear energy endowing with great potential is one of the new energies we are focusing on, since it can not only promote the upgrade of regional industrial structure and accelerate the economic development, but also enhance China’s comprehensive national strength. It is particularly important for coastal and inland areas suffering from energy shortage to actively develop nuclear power. Therefore, speeding up the construction of nuclear power and actively developing such power is a must to protect national energy and is of great significance to the sustainable development of China’s energy and optimization of its energy structure.Taking the Liaoning Hongyanhe nuclear power project under construction as an example, this paper studies the seepage field evolution and mechanical properties of the coastal diversion embankment cofferdam at the construction stage in combination with the characteristics and the actual situations of the project. A comprehensive analysis is carried out from the determination of cofferdam program to the establishment of the model, from the impact of sea waves and ices to the checking computations of the cut-off wall, and from the fluid-structure interaction to the strength reduction and its stability calculation, of which the results will be used to guide the physical works to ensure a safe water diversion projects construction. Details are as follows:1. Summarize the research findings of diversion embankment cofferdam works at home and abroad; establish the thesis content and technology roadmapTo study the seepage and mechanical characteristics of the water diversion projects of Liaodong Gulf Nuclear Power Plant in the construction stage, lots of researches have been done on the development status of the domestic and international diversion works, the seepage mechanism of diversion embankment cofferdam, seepage field and stress field coupling, as well as the seepage technology development of the earth and rock cofferdam, among which the focus is placed on the diversion embankment cofferdam works, researches on its seepage mechanism, analysis technologies of the fluid-structure interaction and anti-seepage methods, etc. The research ideas and implications as well as contents and technical routes have been determined based on the existing domestic and foreign researches. 2. Determine the diversion embankment cofferdam program for water intake; build space model of physical simulationThe Hongyanhe water project requires a large water volume that is supplied to four million-kilowatt generator sets and the nuclear island, therefore, the water safety and reliability are extremely important. In order to reduce the cost by simplifying the facilities, the diversion embankment design program should be studied comparatively based on the natural conditions of the water intake area, as well as the hydrogeological conditions of the project. Select the diversion embankment works and compare the construction cofferdam program according to the actual site; determine the diversion embankment cofferdam program for the water intake and its cutoff wall program. Meanwhile, simulate and mold the diversion embankment cofferdam and tide evolution with finite element modeling software (SolidWorks and Midas\GTS), to present the initial form of water intake appropriate to the on-site construction, build physical model of the water intake, simulate its tide changes and complete the diversion embankment cofferdam simulation and space modeling.3. Effects of coastal diversion embankment cofferdam seepage and sea waves&ices impactBy using Geo-Studio software and finite element model, analyze the seepage characteristics of the diversion embankment cofferdam, impact effects and suction effects of sea waves, and the impact effects of sea-ices; develop the construction methods for anti-seepage as well as diversion embankment cofferdam protection initially.4. Analyze the stability and cut-off wall stress of the diversion embankment cofferdamThe diversion embankment cofferdam of coastal nuclear power plant is an important water retaining structure to ensure the dry construction of water intake structures, thus imposing high requirements on anti-seepage and structural safety. As seepage control, deformation stability control and construction control are crucial to the construction of the diversion embankment cofferdam, it is necessary to check calculation for the mechanical properties and stability of the diversion embankment cofferdam works. Carry out tests on the sand in the foundation of temporary cofferdam and diversion embankment according to the results of the diversion embankment cofferdam foundation tests and analysis of the stability; select and determine the calculation content and earthquake input parameters of the temporary cofferdam and diversion embankment; carry out corresponding stress analysis under static conditions, structure analysis at the Phase Ⅱ construction in case of an earthquake, liquefaction analysis of the sand in the foundation and stability analysis by limit-equilibrium-based pseudo-static method. 5. Analyze the mechanical properties of fluid-structure interaction of the diversion embankment cofferdamThe water diversion projects is located at waters with complex topographic and geologic conditions. Carry out the analysis of seepage of physical diversion embankment cofferdam and mechanical properties of fluid-structure interaction based on the3D physical simulation modeling of the project, so as to further analyze its stability subject to the actual situation and indicating the construction stage. After developing the finite element method for coupling of the seepage field and stress field, and establishing the finite element model of the fluid-structure interaction of DEC, analyze the seepage rules and mechanical properties of such fluid-structure interaction of diversion embankment cofferdam.6. Analyze the effects of strength reduction of cofferdam slopes and earthquakes on the stability; monitor and detect the cofferdam at the construction stage.Analyze the effects of the finite element strength reduction of diversion embankment cofferdam and earthquakes on the stability at the construction stage by Phase2D software and analysis methods of finite element strength reduction and seismic response.After completing the aforesaid analysis and measuring the diversion embankment cofferdam works for control and inspection, determine the purposes and contents of the construction settlement and displacement monitoring:requirements for measuring instruments and measuring levels, settings and requirements of leveling network, plane net and monitoring points, the frequency of monitoring, and the evaluation of the diversion embankment cofferdam works settlement and displacement. Meanwhile, use ground-penetrating radar (GPR) principle and detection methods to detect and evaluate the diversion embankment cofferdam as well as its internal ice water on condition that the processing methods of radar detection data have been developed and GPR wave modes identified. |
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