The world-famous Three Gorges Project (TGP) is the largest hydropower station in the world and also the largest water resources and hydropower project constructed in China. The impoundment of Three Gorges Reservoir reached the design water level of 175 m for the first time on October 26, 2010, which marked that the various functions such as flood control, power generation and navigation of TGP can meet the design requirements. It took nearly 100 years from conception, demonstration, design, construction and operation to final completion of TGP. How was the conception of TGP proposed? What a role it should be? What are different opinions existed? How was the project demonstrated? What was the conclusion of demonstration? Those are the issues that many people care about but do not quite understand. A compendious introduction is made in memory of the achievement of the century dream.
Seeking water and earning their livelihoods is the natural selection of human beings. Like other rivers on the earth, the Yangtze River is the birthplace of human civilization and survival. As an ecosystem, the Yangtze River Basin is evolving under the influences of natural factors and human activities. Because of soil erosion, pollution and human activities, the imbalance of secondary environment is exacerbated and the ecological environment has become more vulnerable. It is urgent to mitigate and prevent the ecological crisis. The practice has proved that implementation of engineering measures is an effective way to improve the ecological environment. The Three Gorges Project (TGP) has a flood control storage capacity of 22.15 billion m3, effectively storing the flood water upstream of Yichang, and protects 15 million people and 1.5 million hm2 farmland. Furthermore, the project can prevent or slow down the sedimentation and shrinkage of the lakes in the middle Yangtze River such as Dongting Lake; with an average annual power generation of about 90 billion kW·h, it can significantly reduce CO2 and harmful gas emission. In general, the construction of TGP is conducive to the ecological and environmental protection in the Yangtze River Basin and China, even the world.
The important role of TGP in the flood control of the Yangtze River Basin is summarized and the "Optimum Regulation Schemes of the Three Gorge Reservoir" is briefly described. In combination with practical flood regulation and operation, the flood regulation effect of TGP is analyzed; several problems related to reservoir flood regulation are discussed and suggestions are put forward for the future work.
The dam of Three Gorges Project is characterized by large flood discharge capacity, more outlets complicated flood discharge and energy dissipation structure etc., the gentle-dip structural plane of the bedrock in powerhouse dam section endangers the dam foundation stability due to the deep excavation of powerhouse at the dam-toe. For the dam body concrete, the durability requirement is high as well as the temperature control and crack prevention are difficult. There is a lack of practical experiences in the design and construction of asphalt concrete core wall for Maopingxi protective earth-rock dam. The power station operates with high water head and large head variation. The type selection of penstock and intake as well as the embedding way of spiral case are complicated in technique, and the tailrace tunnel with sloping ceiling of underground power plant is arranged instead of traditional tailrace surge tank. For the double-line five-step ship-lock, the design of fully lined ship-lock, high head delivery system and large-sized miter gates and hoists is very difficult due to high operation head, complicated delivery conditions and building in deep excavated rock. The preferred solutions, optimal schemes and technical measures for various structures, as well as the innovation achievements proved by practice are highlighted.
Three Gorges Project (TGP), the largest water resources and hydropower project in the world with huge scale and complex techniques, has great comprehensive benefits mainly in flood control, power generation and navigation improvement. Through 16year construction and operation, some valuable experience in the management system and mechanism for hydropower project construction have been gained, and its construction management mode produces important influence on the management system of domestic capital construction. With combination of the construction management practice of TGP, the characteristics of management system and mechanism are summarized, and the suggestions on current hydropower development system and construction management mode are put forward.
In the design, construction and operation periods of the Three Gorges Project (TGP), great challenges have been met in different fields such as water resources and hydropower project construction, electromechanical equipment manufacture and ecological environment protection. In view of the key techniques and difficulties in the construction period, S&T breakthrough have been performed by the experts and scholars of various fields and a series of innovative achievements are gained, which make the scientific and technological levels in relevant fields improved. Some major innovative achievements gained in the TGP construction and operation are enumerated, which are significant for the hydropower project construction and clean energy development in the future in China.
Three Gorges Project (TGP) plays a key role in harnessing and developing the Yangtze River, undertaking the tasks of comprehensive utilization such as flood control, power generation and navigation. After the completion of the project, it can be ensured that the flood control standard of Jingjiang area will be not less than 100-year-frequency. As a result, the flood control pressure on the midlower reaches will be alleviated greatly,great energy support will be provided for the central, east and south China and the navigation conditions of Chuanjiang River will be improved fundamentally. Meanwhile, the navigation channel depth can be increased and the navigation conditions will be improved in the middle river reach through compensating regulation in dry season. In the new era, new requirements have been put forward to the operation of TGP for the harnessing, development and protection of the Yangtze River Basin. How to optimize the water resources utilization and implement a scientific operation to promote the comprehensive benefits of reservoir will be a longterm task of TGP.
The research process, main contents, methods and conclusions for some major engineering geological problems of Three Gorges Project (TGP) are reviewed and introduced, including dam site selection, regional tectonic stability and seismic activity, stability of reservoir bank and reservoirinduced earthquake. Meanwhile, the above mentioned engineering geological problems are evaluated according to the preliminary storage test results since TGP's operation and impoundment in 2003.
The site geological investigation and research work of the Three Gorges Project (TGP) has lasted for more than 50 years, which catches wide attention at home and abroad due to its depth and extent. The research processes, approaches, contents and basic conclusions for the key engineering geological problems of dam site are briefly introduced, including the deep anti-sliding stability of dam foundation, the high slope stability of permanent ship-lock, the surrounding rock mass stability of the main plant of underground powerhouse and the faulted structures. Finally, an overall summarization and evaluation of the research are presented based on the situations of project construction, monitoring and operation.
Since the impoundment of Three Gorges Reservoir in 2003, the construction schedule, resettlement and geological hazard treatment were ahead of those in the preliminary design. The sedimentation conditions were obviously better than expected, and the goal of stage-by-stage impoundment was achieved in advance. Simultaneously, with the changes in operating conditions, optimum operations such as floating control of flood limit water level, medium and small flood regulation and impounding in advance were carried out, which produced enormous comprehensive benefits in flood control, drought relief, navigation, water supply and ecology. Especially during the flood season in 2010, the flood retention and storage capacity reached totaled 26.6 billion m3 through medium and small sized flood regulation, and the flood resources were fully utilized. In the end of the flood season, the flood resources were fully utilized and the water lever reached 175 m first with the joint operation of flood control and water storage. Then the project began to give full play to its comprehensive benefits during the normal operation period.
In order to improve the comprehensive benefits of Three Gorges Project (TGP), the optimal research and practice of planned reservoir regulation mode have been made since the impoundment of Three Gorges Reservoir. Several key techniques are analyzed and summarized, including coordination of multipurpose demands on flood control, power generation, navigation, water supply and ecological protection, risk control of reservoir regulation, optimization of regulation decision and preparation of regulation rules for standardizing the regulation work. The purpose is to seek new ways of improving comprehensive utilization and regulation, so as to realize the maximum economic and social benefits and to make the TGP become an environment-friendly and great transcentury project.
The dam of Three Gorges Project is a concrete gravity dam with the crest elevation of 185 m, the maximum height of 181 m and dam axis length of 2 309.5 m. The dam consists of spillway, powerhouse, non-overflow, ship-lift, temporary ship-lock, left diversion wall and longitudinal cofferdam sections. Some key techniques relating to dam structure design are presented, including hydraulics of flood discharge structure, joint design, layout and structural style of penstock, deep antisliding stability of dam foundation, sealing of temporary ship-lock and closed drainage and pumping of dam foundation.
Using physical model and numerical simulation techniques, some technical problems were studied systematically, including layout of power station, measures of sediment and floating debris discharging, types of intake, embedded types of spiral case, layout of underground powerhouse tunnel group and block reinforcement. It was optimal in technique and economy with the arrangement of powerhouse at the dam-toe of both banks + underground powerhouse in the right bank, as well as the intake with a single and small orifice. The sediment and debris problems could be solved with disperse sediment ejection and floating debris discharging holes. With the adoption of techniques for spiral case such as heat and pressure preservation, cushion layer and combined embedding, the stable operation of generating units can be guaranteed. The arrangement of tailrace tunnel with sloping ceiling was better than that of tailrace surge tank. The technical requirements related to the embedding type of spiral case were proposed. The reinforcement of huge unfavorable blocks was discussed and the new idea for block reinforcement using anti-sliding piles and normal compressive stress of structural plane was put forward.
The general design and layout of the double line five step ship lock , the water delivery technique for high head ship lock, the key technical problems of fully lined ship-lock and the monitoring techniques for large scale miter gates and hoisting equipment under complicated operation conditions of the Three Gorges Project (TGP) are introduced. Since the operation of ship lock in 2003, the operation practice has proved that the design techniques are advanced, rational and reliable. The design and construction of the fully lined ship lock promotes the development of design theory and practice of ship lock projects, which makes the construction technology of ship lock in the world reach a new level.
The double-line five-step ship-lock of Three Gorges Project is an extra-large navigation structure with the maximum design total head and single-step delivery head in the world and complicated technical problems. The ship-lock is a challenging and world-class project integrating the advanced techniques and equipment, the up-to-date technologies and materials, as well as the advanced project management. Through 17-year construction and 9-year operation of the ship-lock, various difficulties in design, construction, equipment manufacturing and installation as well as system debugging have been overcome effectively. The project management ideas, management system, management methods, technological innovation and team building are summarized according to the management practice of the second stage main works of Three Gorges ship-lock.
The Three Gorges ship lift is the largest and the most difficult one in the world with the characteristics of large lifting weight, high lift range, big fluctuation of water stage between upper and lower reaches and quick variation of navigable water level. After scheme comparison, the gear rack climbing type ship lift is selected, which is characterized by complicated structure of facilities and high precision requirements of manufacture, installation and construction. Meanwhile the Sino German co design method is first adopted. The general layout of gear rack climbing type ship lift, as well as the design schemes and key techniques of tower structure and important equipment are briefly introduced.
In view of the specified design conditions of Three Gorges Project (TGP), the main technical problems that should be considered in the design of hydro turbine generating units are analyzed. The key technical researches performed are summarized and the parameters of hydro turbine generating units are optimized through the study on key technical problems. The unit operation results indicate that the performance of the hydro turbine generating units is excellent, and the units can operate in a safe, stable and highly efficient mode for a long term. Therefore, it is verified effectively that the general technical design of giant hydro turbine generating units is scientific and rational.
The construction of Three Gorges Project (TGP) is characterized by large construction scale, high construction intensity and complexity in technology. In view of various technical difficulties such as navigation in construction period,Changjiang river closures, high intensity concrete and earth rock construction,roller compacted concrete (RCC) cofferdam in 3-stage III and double line five step ship lock,the general arrangement of the project construction is as follows:construction in 3-stage,navigation with diversion channel and power generation under cofferdam project.The practice and innovation achievements in river diversion during construction as well as earth rock and concrete construction were presented emphatically.
Based on 17 year monitoring data of the Three Gorges Project (TGP), the change laws of deformation, seepage flow and pressure, as well as stress and strain of the main structures in the period of construction and operation are discussed. Meanwhile, the operational status and safety features of various structures in different construction stages and under different circumstances are analyzed and evaluated in detail. The monitoring results show that the repeated rise and fall of reservoir water level affect the deformation of dam in storage and operation stages; the leakage of dam foundation reduces gradually; the high intensity excavation unloading influences the deformation of high rock slope significantly. After the excavation, the deformation of high rock slope rapidly decreases,while the deformation of ship lock is small,but they all vary with temperature obviously. It is concluded that the safety indexes of TGP are within the allowable range of design and the structures are safe in operation.
The key to success of Three Gorges Project is the migrant resettlement, while the resettlement planning and effective organization management is the guarantee of smooth implementation of resettlement. In the process of resettlement planning and implementation, through the establishment of systematic legislation and document support system, introduction of environmental capacity analysis and assets appraisal methods, the scientific site selection, and correct grasp of the relationship between resettlement compensation and local development, preparation of reasonable resettlement schedules are carried out; through the establishment of efficient management system and capital management mode of "static control and dynamic management", as well as the timely adjustment of plan according to actual conditions, the resettlement is completed smoothly. Therefore, the social stability of reservoir area is ensured. The economic development of reservoir area is promoted and the improvement of legislation, regulations and techniques for land requisition and resettlement is promoted. The theory and prospective work of resettlement are discussed.
According to the measured data after impoundment and operation of the Three Gorges Reservoir, the reservoir sediment deposition and downstream river channel scouring are described briefly and compared with the research results achieved in the demonstration stage. It is indicated through analysis that the reservoir sediment deposition and downstream river channel scouring during 8-year impoundment and operation are still within the original forecast, so the original forecasting results are feasible. The further observation and comparison should be conducted because the comparison between the observed data and the original forecast is not so sufficient in time and the prototype observation and related research work should be strengthened in the future.