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Since the 21st century, marked by the operation of the Three Gorges Project and the South-to-North Water Diversion Project, China has entered the fourth stage of independent innovation and leading development. The successively completed Xiaowan, Longtan, Shuibuya, The construction technology of Jinping Class I and other projects continues to set world records. At this stage, China pays more attention to the safety of giant projects and ultra-high dams, and pays attention to environmental protection. It is an international leader in many fields. At the same time, it also fully participates in the international water conservancy and hydropower construction market, with more than half of the international market share.

As of 2014, China has built more than 98,000 reservoirs of various types, with a total storage capacity of 8.166×1011m3, reaching 29% of the national rivers’ annual runoff; the effective irrigation area of ​​farmland reached 6.9×107hm2, accounting for 23% of the world; There are 6539 dams under construction and over 30m in height, accounting for 43% of the world’s total; the total installed hydropower capacity has exceeded 3×108kW, accounting for 27% of the world’s total; the total installed capacity of pumped-storage power stations already built is 2.211×107kW , Accounting for 12% of the world; the length of the main water canal exceeds 1.38×104km, and the length of the hydraulic tunnel exceeds 1×104km. China has become the country with the largest number of reservoirs and dams, the largest farmland irrigation area, the largest total installed hydropower capacity, and the longest water transfer project mileage in the world. The comparison with the international situation is shown in the figure1. Figure 2 and Table 1 to Table 3.

Figure 1 Number of dams over 30m high in major countries in the world

Figure 2 Pumped storage installed capacity of major countries in the world

Table 1 Top 10 Dams in the World by High Dam

Table 2 Top 10 reservoirs in the world by storage capacity

The largest reservoir in China is the Three Gorges Reservoir with a storage capacity of 4.505 × 1010 m3, ranked the 24th in the world.

Table 3 Top 10 projects in the world with installed capacity

China has built the world’s most water conservancy and hydropower projects, and has adopted the most stringent water resources management system, requiring water to determine the city and water production. However, due to the large population and uneven distribution of water resources in time and space Compared with developed countries, it is still necessary to continue to promote project construction.

Based on data from about 100 countries, we compared the relationship between water resources development and the Human Development Index (HDI)(Picture 3, Picture 4), HDI is an important indicator to measure a country’s comprehensive national strength. It can be seen that developed countries have high human development index (life expectancy, education level, GDP per capita), and the corresponding water resources development are generally high.

In 2014, China’s Human Development Index was 0.727.The electricity development rate is 52%, and the per capita storage capacity is about 600 m3, which is basically in line with the indicators of more developed developing countries, indicating that China’s reservoir and hydropower construction is generally in harmony with the level of national economic and social development.

Figure 3 Relationship between Hydropower Development Degree and Human Development Index

Figure 4 Relationship between per capita storage capacity and human development index

Second, dam construction safety assurance technology

The development of China’s earth-rock dams, gravity dams, arch dams, and cemented particle dams have been detailed in the literature. In the construction of high dams, China pays special attention to safety and has developed many new concepts and technologies.

(1) Realistic simulation of high concrete dam, high-pressure water splitting resistance and material preparation

Concrete dams are one of the main types of high dams in the world. Among high dams above 200m, it accounts for more than 60%, and in China it accounts for 56%. In order to develop water resources, a series of high concrete dams will be built around the world, so ensuring the safety of high dams is of great significance.

The development of high concrete dams in the 20th century made great achievementsAt the same time, there are painful lessons. The construction of high concrete dams such as Hoover, Incoulee, Grand Dixon and Itaipu has made outstanding achievements, leading the development of high concrete dams. High dams such as Coenbrien(Picture 5) in Austria, Dvorak in the United States, and Sayanshushensk in the former Soviet Union have all experienced serious cracking and water leakage The cost of repair and reinforcement is huge; the Malpasay arch dam in France collapsed due to the instability of the dam abutment, causing huge losses to life and property; China also has instances of serious cracks in high concrete dams and high-pressure water splitting that affect safety.

Many accidents show that traditional calculation methods and construction techniques cannot meet the needs of safe construction of high concrete dams. The main manifestations are:

①The stress, deformation, and stability calculated by the traditional method are quite different from the real situation, and the dam behavior prediction error is large;

②The contradiction between the high strength and high crack resistance of dam materials is prominent, and it is difficult to take into account the traditional method of preparation;

③The risk of high-pressure water splitting in high concrete dams is high, and the damage after splitting is serious.

Figure 5 Coenbryan Arch Dam accident and reinforcement

In order to realize the “predictable behavior, safe and controllable” of the dam, based on the analysis of the stress and cracking range of 15 typical arch dams built at home and abroad, the finite element and other effects suitable for 300m-level super high dams are proposed Force method and stress control standards, and proposed a time-history dynamic stability analysis method for deformable bodies. An improved dynamic contact force model is used to simulate the nonlinearity of opening, adhesion and slippage of each sliding surface of the dam foundation rock mass under static and seismic forces. In terms of mechanical behavior, a new quantitative evaluation criterion of local deformation accumulation reaching a critical state and an inflection point of controlled displacement is proposed, and a new evaluation system for dam stability and dam ultimate seismic capacity is established.

Traditional methods have large errors in predicting the behavior of dams, and the difference between the predicted displacement value and the observation result is commonAbove 30%, the stress state of the dam heel is sometimes opposite to the observed value, which makes it difficult to accurately assess the safety state of the dam. my country has proposed a post-temperature rise model for high concrete dams, created a multi-slit dam efficient iterative model and a mezzanine replacement hole column model for drainage hole screen simulation, and realized concrete dam pouring, grouting, water storage operation, and aging and deteriorating construction Running the whole process simulation has significantly improved the prediction accuracy of dam behavior.

Predicted maximum deformation value of ultra-high arch dams such as Xiaowan, Jinping I and Dagangshan at the initial impoundment to normal impoundment level (3 Month) The errors of the monitored value are 0.9%, 0.1% and 2.2%, which are much smaller than the error between the calculated value and the monitored value by the traditional method. (respectively 36.6%, 76.1%, 36.4%).

In order to realize the resistance to high-pressure water splitting, invented the full-graded concrete high-pressure water splitting simulation test method and device. It is proved that both the design of ultra-high gravity dams above 200m according to the non-tensile stress criterion and the compressive stress criterion There is a risk of high-pressure water splitting, and the design methods and criteria for resisting high-pressure water splitting are proposed. Invented the flexible anti-seepage structure of the high concrete dam surface and the anti-seepage structure in front of the dam, and invented the simulation test device, which proved that under the action of the 300m water head, the cracks of the dam heel concrete can be prevented from splitting by high-pressure water. The proposed flexible anti-seepage and self-reflection filter structure in front of the dam is more reliable than adding apron.

The Hoover Dam in the United States uses low-heat Portland cement, and the cost of concrete per cubic meter is more than 30% higher than that of the Three Gorges, which is difficult to imitate. In order to ensure the safe construction of the “Millennium Plan” Three Gorges Project and 200m high concrete dams, the close accumulation of multiple cementing powders and the composite cementing effect were discovered, and a new method of preparing high dam concrete was proposed, which solved the traditional method of preparing concrete. The difficult problem of both high strength and high crack resistance has opened a precedent for the large-scale use of Class I fly ash and limestone powder admixtures in high dam projects.

Applied to the 4×106 m3 concrete in the third phase of the Three Gorges Project, the anti-cracking coefficient increased by 13.1%~50.0%. It can be seen from Figure 6 that when the content of ultrafine powder (MF) reaches 20%~40% of gelled powder, the water consumption of slurry can be reduced by 12%. , Which can greatly reduce the concrete water consumption and cementing material consumption.

(2) Deformation coordinated control and dynamic stability design of concrete face rockfill dam

The construction of modern face rockfill dams started in 1965, represented by Cooke, emphasizing the design based on experience, small-tonnage vibratory rolling and thin-layer rolling construction. China began to introduce modern face-faced rockfill dam technology in the 1980s, and later developed the control panel structural cracks. Chinese and Brazilian experts proposed the concept of dam deformation control and applied it to Shuibuya , Hongjiadu and other projects.

China has put forward strict indicators for porosity control. Rolling equipment with greater excitation force is used to control the porosity of rockfill materials at 19%-20%, and the maximum settlement deformation of the dam is controlled at 1% of the dam height. See Table 4 for details. Pinto believes that increasing the compressive modulus E of the rockfill body is the most effective to reduce the compressive strain of the slab, and established the relationship between the deformation modulus E/(γH) of the rockfill dam and the valley shape factor A/H2(Figure 7). The above-mentioned knowledge and practice promoted the development of concrete faced rockfill dam.

Figure 6 Test results of relative water consumption of standard consistency

Figure 7 The relationship between the deformation modulus of the rockfill dam and the valley shape factor

On the basis of Pinto’s original map, 10 concrete faced rockfill dams such as Shuibuya have been added. It can be seen that Shuibuya, Bagun and other concrete faced rockfill dams do not meetPinto concluded that it is not scientific to control the deformation of the rockfill body alone. It is a reasonable way to control both the total deformation of the rockfill body and the coordination of various parts of the deformation.

Combined with the construction of Bakun face rockfill dam and other projects, a new concept of deformation coordination design was proposed, and the deformation coordination criteria, judgment standards and deformation safety design calculation methods were established, and the operation of typical projects designed according to the new and old concepts See Table 4.

Table 4 Statistical data of typical high face rockfill dams at home and abroad

In the early development process of the high-face rockfill dam, there has always been the problem of damage to the peripheral joints and water leakage. Combined with the construction of the Shuibuya face-faced rockfill dam, the research proposed a new water-stop structure, and later summarized the design concept of dynamic and stable water-stop . The basic requirement is that under the high water pressure of 300 m, the water-stop structure can withstand three-way large displacement, and form a stable water-stop system through dynamic self-adjustment, that is, the new water-stop structure can achieve dynamic performance under normal design conditions. Stable water stop, and can rely on new materials with flowing water stop function to make up for the defects of the water stop system under extraordinary circumstances.

See Table 5 for the operational effects of the new water stop design and foreign conventional water stop design projects. The leakage evaluation method of the face rockfill dam was established by using the face-face comprehensive permeability coefficient method. Based on the monitoring results of 67 face-face rockfill dam projects at home and abroad, Figure 8 is obtained. The Shuibuya and Hongjiadu projects are all located in high-quality areas.

Table 5 Comparison of water stopping effect at home and abroad

Figure 8 The cumulative probability curve of the comprehensive permeability coefficient of the panel

(3) High dam seismic safety

In the Hoover Arch Dam demonstration, the U.S. Bureau of Reclamation has developed a test load method, which considers the earthquake acceleration of 0.1g for seismic fortification according to the pseudo-static method. Subsequent progress includes the dynamic characteristics and dynamic response analysis of the arch dam based on the trial load method. China is building high dams above 200m in strong earthquake areas, and the design seismic acceleration values ​​are generally large. For example, the Xiaowan Arch Dam is 0. 308g, the Xiluodu Arch Dam is 0. 357g, and the Dagangshan Arch Dam is 0. 5575g(Currently the highest design value of concrete dams in the world).

The team represented by academicians Chen Houqun, Zhang Chuhan, and Lin Gao has developed and established a systematic method for the seismic safety analysis of concrete dams, which mainly include ground motion input, structural seismic response, and structural resistance analysis.

The random finite fault method is used to consider the ground motion input characteristics of near-field large earthquakes with the surface source rupture process, and the “effective peak acceleration” corresponding to the ground motion acceleration response spectrum is adopted.(EPA) is the main seismic design parameter that characterizes the intensity of earthquake action. The probability method is combined with the deterministic method, and the design seismic response spectrum is determined by the set earthquake.

The time-history dynamic stability analysis method of the deformable body coupled with the dam body and the foundation is proposed, and the new quantitative evaluation criterion of the local deformation accumulation reaching the critical state and the sudden change of the control point displacement is proposed, and the overall stability and large scale of the dam are established. The evaluation system for the ultimate seismic capacity of the dam, the creation of high dam parallel computing technology, the development of parallel computing software, and the establishment of a large-scale three-way six-selfSimulate shaking table by earthquake.

Proposed a concrete damage model that considers both residual deformation and stiffness reduction, and introduced “apparent elastic modulus” (Figure 9) and “visual “Damage factor” establishes the dynamic damage constitutive relationship of concrete[Equation (1)], and applies it to the Shapai arch dam that has withstood the Wenchuan earthquake. Earthquake inspection.

In the Wenchuan earthquake in 2008, four high dams over 100m above, including the Shapai Arch Dam and the Zipingpa Concrete Face Rockfill Dam, have undergone strong earthquake tests, and the dams are overall stable.

Figure 9 The stress-strain relationship of the apparent elastic modulus E-

(4) High dam flood discharge and energy dissipation

China’s large-scale projects such as Xiaowan, Ertan, and Xiaolangdi have high water heads, large flows, narrow river valleys, and complex topographic and geological conditions. Their flood discharge mechanical indicators such as water head, discharge volume, and flood discharge power have reached the highest in the world. Flood discharge and energy dissipation are very difficult.

In response to the problem of flood discharge, energy dissipation and scour prevention for high arch dams, the principle and thinking of “multiple facilities, dispersed flood discharge; double-layer porous, water impact; partition energy dissipation, on-demand protection” was proposed, which was initially successful in Ertan Hydropower Station application. thisLater, with the further development of China’s dam construction technology, the technical parameters of the dam’s flood discharge and energy dissipation have further breakthroughs, as shown in Table 6. These projects all adopted the “two-tank model of dam orifice + flood discharge tunnel + plunge pool energy dissipation”, which solved the problem of high dam flood discharge and energy dissipation. The completed projects are all running well.

Table 6 Some high arch dams at home and abroad flood discharge mechanics index

Based on the concept of “longitudinal diffusion, air friction aeration and energy dissipation”, narrow gap energy dissipation technology has been developed and successfully solved the flood and energy dissipation problems of a group of “narrow valleys, high dams, and large discharge” large-scale projects. The narrow slot energy dissipater has been systematically studied, and the application conditions, design steps and energy dissipation characteristics of the narrow slot energy dissipater have been put forward, which have been successfully applied in large projects such as Longyangxia and Laxiwa.

In order to solve the problems of high water head, large single-width flow, and low Fro’s number flood discharge and energy dissipation, the wide-tail pier stilling pool combined energy dissipater was invented, which was applied to many projects such as Jinghong and Wuqiangxi. The maximum dam height of Jinghong is 108m, and the maximum single-width discharge is 331 m3·s-1, which is the highest level of application of the combined energy dissipater of the wide-tail pier stilling pool so far. In addition, various forms of internal energy dissipation technology such as orifice plate energy dissipaters and cyclone energy dissipators have been developed to solve the problem of water flow connection between diversion tunnels and flood discharge tunnels, and at the same time, there is no adverse impact on the environment caused by the spray atomization. , Successfully applied to Xiaolangdi, Gongboxia and other projects.

The topography and geological conditions of the deep mountain and canyon area often bring difficulties to the layout of the spillway tunnel of the hydropower station. The “Long Luowei” spillway tunnel layout idea and the flood tunnel aeration reduction technology proposed by the study can reduce the risk of high-speed water cavitation damage Significantly lower, it has been successfully used in Xiluodu, Jinping I and other projects.

3. River governance and the theory of uneven and unbalanced sediment transport

China’s Yellow River and Yangtze River are world-renowned, but governance is the most difficult. Figure 10 compares the decline of typical international rivers. Take the Yellow River as an example. Before 1949, it was a river that changed course once in a hundred years and broke twice in three years.A serious disaster. The flow of the Yellow River varies greatly during the four seasons, the sediment content is high, and the reservoir siltation problem is serious.

The annual sediment transport volume of the Yellow River is 1.6×109t, 1.8 times that of the Amazon River’s annual sediment transport volume of 9×108t, and the annual average sediment concentration is 35kg·m–3, which is 210 times that of the Amazon River. A survey in 1992 showed that more than 20% of the reservoir capacity in the Yellow River Basin had been silted. In this regard, methods such as “storage and discharge of muddy” and “density flow and sand discharge” have been adopted to achieve the Yellow River governance goal of “no siltation, no crevasse, continuous flow, and no deterioration of water quality”.

Figure 10 Comparison of gradients of typical international rivers

Because of the high sand content and serious siltation of the river, the lower reaches of the Yellow River have become a suspended river above the Huanghuaihai Plain. In order to deal with the water and sand disasters of the Yellow River, Hu Chunhong et al. proposed an overall river-wide spatial optimal allocation framework, and constructed a theory and model for the optimal allocation of sediments in the Yellow River. Relevant management departments have put forward water and sediment regulation models such as “based on Xiaolangdi Reservoir single reservoir regulation, spatial scale water and sediment docking, and main stream reservoir group water and sediment joint regulation”, forming a water and sediment regulation theory and index system< /strong>.