1, overview
Danjiangkou Water Control Project is located on the main stream of Hanjiang River in danjiangkou city, Hubei Province. It has comprehensive benefits such as flood control, water supply, power generation and shipping. It is a pivotal project for developing and harnessing the Han River, and also a water source project for the Middle Route of South-to-North Water Transfer Project. According to the actual situation of project planning and construction, Danjiangkou water control project is developed and constructed in two phases.
The normal water level of the initial project is 157m, and the corresponding storage capacity is174.5 billion m3. The once-in-a-century flood level is 16 1.45m, and the corresponding storage capacity is 20.97 billion m3. Dam crest elevation 162m, consisting of left and right bank earth-rock dams, left and right bank concrete non-overflow dams, deep hole dams, surface hole dams, power stations and ship lifts. The total length of the retaining dam is 2468m, and the concrete dam is a gravity dam with wide joints, with a total length of 1 14 1m and a maximum dam height of 97 m. The length of the earth-rock dam on the right bank is130m, and the maximum dam height is 32m. . The length of the earth-rock dam on the left bank is 1 197m, and the maximum dam height is 56m, all of which are clay core dams. The initial project was officially started in September 1958, and the dam began to stop flood in June, 1 1, and the first unit generated electricity in June, 1968. The underwater part of the riverbed concrete dam has been completed according to the final scale, 1977.
The second phase includes heightening earth dam and concrete dam. According to the project plan, the elevation of the dam crest is 14.6m to 176.6m, and the total length of the water retaining structure is 3442m. In order to meet the requirements of dam stability and stress during water retaining, cast-in-place concrete is used to increase the height and thickness of the concrete dam crest and downstream slope, and the length is still114. The crest of spillway of concrete dam is raised to the elevation of 152m, and the maximum dam height of concrete dam is 1 17m. The earth-rock dam on the right bank was rerouted and rebuilt, with a length of 877m and a maximum dam height of 60 m. The earth-rock dam on the left bank was raised and thickened, and the left abutment extended to the left for 200m, with a length of 1424m and a maximum dam height of 71.6 m. The installed capacity and layout of the power station remained unchanged. Navigation structure was expanded from the original 150 ton ship lift to a 300 ton ship lift, and the overall layout remained unchanged.
2. The contradiction between operation management and dam heightening construction.
2. 1 Construction and operation are parallel, and the traffic in the field interferes with each other.
Because the dam heightening construction is carried out on the basis of the original dam, the construction site is narrow and the traffic is very crowded due to the limitation of the original dam structure and the geographical location of the river bed. During the heightening construction of the dam, the transportation of raw materials, machinery and equipment and the commuting of construction personnel mostly pass through the original dam road, and the construction occupies the original dam crest site, which adversely affects the transportation of materials and equipment for dam operation management, the walking of electromechanical equipment such as hoists, the daily inspection of hubs and the normal maintenance and overhaul of hydraulic structures, resulting in difficulties in operation management and maintenance.
2.2 The contradiction between dam maintenance and the second-phase project construction
The maintenance and repair of the dam is an important work to ensure the safety of the dam. Dam heightening construction is not conducive to normal maintenance work, which may lead to delay or failure of maintenance work. On the other hand, the maintenance repairman will also have a certain impact on the construction of the second phase project, which may cause some single projects to be postponed or the construction quality cannot be guaranteed.
2.3 The contradiction between the addition and reconstruction of normal dam monitoring and observation facilities and the construction of the second phase of the project
The horizontal displacement monitoring facilities of Danjiangkou Dam have 25 vertical lines (including 12 inverted vertical lines), 3 tension lines, 2 precision traverse lines and 29 measuring points. There are 363 vertical displacement monitoring points. During the heightening project, most of the monitoring facilities in the concrete dam continue to maintain their original working methods. However, the change of dam structure in the later stage will affect some monitoring facilities in the dam, and the measuring points in contact with the top surface of the dam will also be affected, and some monitoring projects will stop. At the same time, the normal monitoring work, the transformation of monitoring facilities and the protection and connection of monitoring facilities during the construction process will also have some adverse effects on the heightening construction.
2.4 contradiction between dam flood control and construction
During the heightening construction of Danjiangkou dam, the hub still undertakes the flood control task in the middle and lower reaches of the Han River, and it is necessary to ensure the dam safety and flood control safety in the middle and lower reaches of the Han River. The flood control standard for construction adopts the once-in-a-thousand-year flood, which is the same as the design flood standard for the initial project. The spillway dam section of Danjiangkou Water Control Project is mainly used to open floodgates and discharge water when the water level in front of the dam exceeds the specified flood limit level or normal water level. During heightening project 1 ~ 3 years dry season, dam slope construction is mainly carried out. According to the stress requirements of the dam structure during the construction period, the water level of the reservoir should not be higher than 152m, and the limited water level in the next two years will be145m. The frequent use of flood discharge opening and closing equipment increases the workload of flood discharge facilities.
The normal flood season of the hub will have a great impact on the heightening construction of Danjiangkou dam, mainly due to the interaction between the construction of flood discharge structures and the flood season of the hub. According to the preliminary design scheme, the weir hole will be constructed in the dry season of 10 from June to April of the following year. According to historical records and statistical data, the probability of flood after 10 in Hanjiang River Basin is high. According to the dispatching regulations, when the hub encounters a once-in-a-century flood or more, all weir holes should participate in flood discharge. If the weir hole construction is carried out during this period, on the one hand, the weir hole can not participate in flood discharge normally, and the flood discharge capacity of the hub is greatly reduced, which poses a threat to the safety of the hub. On the other hand, the unfinished weir hole construction will also be forced to stop, forming structural joints that are not originally designed, and the overflow surface at the top of the weir will be washed away by high-speed water flow, making it difficult to guarantee the construction quality. In addition, if the downstream of 8 ~ 13 deep-hole dam section encounters deep-hole flood discharge, the construction may not continue, and cold joints will be formed during the construction, which will reduce the pouring quality of dam slope.
2.5 contradiction between power generation and construction limited water level during reservoir operation
In principle, the lower the reservoir water level, the better. However, considering the requirements of the existing initial operation function, when pouring concrete on the slope, the water level of the reservoir should be limited below 1.52m to obtain a better initial displacement value of the dam. When the limited water level is 152m after the flood season in the first three years of the construction period, the annual power generation will be reduced by1980,000 kw·h；; ; In recent two years, the limited water level in flood season was 1.45m, and the annual power generation decreased by 1.65 billion kw h. ..
The flood in Hanjiang river basin is characterized by flash floods, and the intensity of rainstorm is high. The middle and upper reaches are often in the same rainstorm area. The fan-shaped water system flows into the flood along the main stream, and the runoff during the year is extremely uneven. Flood peak and flood volume may occur in a short time. In addition, during the construction period, the flood discharge capacity may be reduced, the water level may exceed the construction limit, and the construction conditions such as dam stress may not meet the construction technical requirements, which may lead to the occurrence of construction quality accidents. Although the method of increasing pre-discharge can improve the safety of construction, excessive pre-discharge will greatly reduce the benefit of the reservoir.
Due to the change of the control water level in front of the dam in flood season, the dispatching regulation of Danjiangkou water control project should be adjusted accordingly. On the one hand, in order to ensure the effective performance of the hub, it is hoped to raise the water level as much as possible, on the other hand, in order to ensure the construction quality, it is required to lower the water level of the reservoir as much as possible. There will be some contradictions between the two.
3. Countermeasures and suggestions
3. 1 Make preparations.
In order to minimize the impact of the second-phase project construction on the hub management, relevant preparations should be made before the main project starts, mainly including the preparatory work that must be completed before the heightening construction of the main dam, land acquisition by immigrants, construction planning, organization and coordination, etc. Whether the preparatory work is sufficient is of great significance for reducing the engineering quantity, reducing the construction interference and contradiction, improving the construction quality and improving the construction management level.
Since 1995, Hanjiang Group has done a lot of preparatory work for dam heightening, and completed the preliminary work of dam heightening, such as the restoration of the original dam axis, the heightening and reinforcement of Wangdagou filter, the connection of sluice slot and the repair of deep-hole breast wall. The author believes that the renovation and reconstruction projects such as the four-way leveling project and the replacement of deep-hole hoist, which can precede the main project construction, should be implemented as soon as possible.
At present, there are still a lot of preliminary work to be done immediately, mainly including the reconstruction of auxiliary facilities such as sand and gravel production system and concrete mixing system, as well as the construction of water supply, power supply, gas supply and communication, and site leveling. In addition, do a good job in immigration and land acquisition in advance to reduce construction disputes. It is also necessary to study the construction progress, construction sequence, zoning and resource allocation according to the actual situation to ensure orderly construction, balanced strength and optimal resource allocation.
3.2 Take various measures to improve traffic conditions.
In view of the congestion in the construction site, the author thinks that various measures should be taken to comprehensively solve it, mainly including: 1) formulating the access system to prevent irrelevant vehicles and personnel from entering and leaving the dam area. 2) At present, the roads on the dam are narrow, there are many turns, there are no traffic lights, and there are many vehicles during construction, which is easy to cause traffic jams and even traffic accidents. It is suggested that the existing roads should be rebuilt and widened, traffic signs such as traffic lights should be added, and road patrol inspectors and road maintenance personnel should be added during the construction period; 3) Strengthen the construction dispatching command, control the traffic flow as much as possible, reduce the construction transportation peak, and ensure the balanced construction transportation intensity; 4) The project legal person shall establish an effective transportation management mechanism, formulate the corresponding transportation management system, and sign a letter of responsibility with each construction unit in the form of contract. 5) Actively take various measures to carry out multi-directional transportation roads, such as building construction bridges, and using Upright to divert the traffic flow on the left and right banks and upstream and downstream of the dam.
3.3 Improve the construction mechanism of operation management, establish corresponding rules and regulations, and standardize management.
3.3. 1 Revise and formulate relevant rules and regulations. Rules and regulations on construction and operation management should be promulgated as soon as possible. The contents of rules and regulations should mainly include: ① setting the boundaries of working areas to separate operation, maintenance and management from construction; (2) Assign full-time coordination and inspection personnel, strengthen on-site management, and do a good job in coordination; (3) Establish information channels, and try to avoid the construction peak in operation and maintenance; (4) Establish dam construction management measures and implement standardized management; ⑤ Actively encourage the optimization of construction and schedule to improve the scientific and technological content of construction; ⑥ The construction party and the operation management party should carry out civilized construction and civilized operation, establish good relations and promote the smooth progress of construction.
3.3.2 Establish a coordination mechanism to realize the sharing of information resources * * * The heightening project construction is different from the general project construction, which is limited by the operation and management of the hub and the construction site, and the construction interference is great, involving many units and personnel. Therefore, it is necessary for the project legal person to take the lead and all relevant units to form a coordination leading group to form a corresponding management mechanism. The main duties of the coordination team are to handle the contradiction between construction and operation management in time, inform relevant parties of construction information and operation management information in time, do a good job of coordination, adjust the progress of construction and operation management in a timely and flexible manner, reduce mutual interference, and ensure that construction and operation management work are staggered as much as possible.
3.3.3 Applying information technology to operation management Information technology has been widely used in various disciplines of water conservancy. In order to improve the level of operation management and construction quality, network technology and digital technology should be actively and widely used. For example, advanced technologies such as RS, GIS and GPS can be used to reduce the interference between construction and operation management and improve the accuracy and efficiency of dam monitoring and construction survey; Establish and improve the computer network system of hydrological database and hydrological information to provide more accurate and timely real-time data for the second phase project construction and flood control of the hub; The establishment of computer local area network makes the collection, transmission and processing of dam heightening construction and hub operation management information faster and more accurate, realizes information sharing, and further improves the construction management level of unified scheduling of construction operation and timely handling related construction problems.
3.4 Improve the forecast accuracy and optimize the reservoir operation scheme.
Meteorological and hydrological forecast is the main basis for guiding construction and flood control, and it is also an important basic work to ensure construction quality. The accuracy of meteorological and hydrological forecasting is affected by the quality of personnel, equipment and forecasting technology. Therefore, we should strengthen the training of technicians, improve the overall quality, update the existing equipment, actively introduce new technologies, develop towards automation, strengthen cooperation with the state, the Ministry of Water Resources and other professional departments, establish cooperation fields, carry out scientific research, realize information sharing, and raise meteorological and hydrological forecasting to a new level.
Through calculation and research, the existing initial project scheduling scheme of Danjiangkou Water Control Project is constantly revised and improved in practice, so that the scheduling rules can truly meet the safe and efficient utilization of the reservoir. According to the flood situation and construction requirements, timely and dynamically control the water level, scientifically and reasonably dispatch, do a good job in reservoir flood regulation calculus, pre-discharge the reservoir water and empty the storage capacity according to the actual flood discharge capacity, which not only ensures that the flood can be discharged in time during the flood, but also controls the water level below 152m, which not only meets the construction requirements, but also does not cause excessive loss of power generation benefits.
3.5 properly handle the relationship between monitoring work and the reconstruction and construction of monitoring facilities.
Corresponding treatment measures should be taken to properly handle the relationship between the two, improve the safety monitoring performance of the dam, reflect the working performance of the dam in real time, guide the construction, and improve the construction quality of the main project and monitoring facilities. The author thinks that the following measures should be taken: 1) In view of the reduction of some monitoring items, in order to accurately reflect the changes caused by dam working behavior and construction, the observation frequency of monitoring items such as vertical displacement of dam foundation should be appropriately encrypted; 2) Some monitoring facilities, such as monitoring cables, conduits, piezometers, etc., should be extended upward with the heightening of the dam body, and should be reserved and maintained during construction to avoid omission or damage; 3) Strengthen the training of monitoring personnel, improve the professional level, and conduct accurate and timely monitoring. 4) In view of the suspension of some monitoring projects, the patrol inspection force should be strengthened to ensure the normal and safe operation and construction of the dam; 5) Standardize the construction behavior through contracts and systems. In order to avoid damage to observation facilities in order to grab the construction progress during construction.
3.6 Actively introduce new technologies, new processes, new materials and new equipment, and vigorously carry out construction scientific research.
In order to improve the construction efficiency and reduce the interference of construction on operation management, we should actively study the new technologies, new processes, new materials and new equipment in today's water conservancy project construction and apply them according to the actual situation of the project construction. For example, the MQ 1800 cylindrical bridge crane developed by Beijing He Jiang Electrical Equipment Engineering Company of the Ministry of Water Resources and designed by Hangzhou Machinery Design and Research Institute of the Ministry of Water Resources can be selected for the heightening construction of concrete in the riverbed dam section. The crane has a maximum working range of 70m and a maximum lifting capacity of 20t, with simple structure, light deadweight and good economic performance, which can meet the needs of concrete heightening construction of Danjiangkou Dam.
According to the actual situation, we should also vigorously carry out construction scientific research, improve construction methods, optimize construction design, improve construction technology level, shorten construction period and reduce the impact on hub operation and management.
3.7 Establish and improve the modern water conservancy construction system
By establishing modern water conservancy construction system, high-level engineering construction management, construction technology and efficiency can be effectively guaranteed, and the adverse impact of construction on operation management can also be reduced.
Danjiangkou dam heightening project should actively implement the "four systems" of project construction according to the requirements of modern water conservancy construction system, namely, the project legal person responsibility system, the bidding contract system, the project construction supervision system and the contract management system. Entrusted by the state, the legal person of the construction project shall be fully responsible for the Danjiangkou dam project construction and introduce the competition mechanism in accordance with the laws and regulations of the State, such as the Bidding Law of People's Republic of China (PRC) and the Measures for Bidding of Construction Projects, in accordance with the principles of "openness, fairness and justice", and following the laws of market economy. Convene experts with rich experience in water conservancy construction to form a bidding committee or entrust a bidding agency specializing in water conservancy, and select domestic construction contractors, construction supervisors, domestic and foreign equipment manufacturers and material suppliers with high enterprise qualification level, good reputation, rich construction experience, high technical level, reasonable construction organization design and sound quality management system to participate in Danjiangkou Dam project through bidding.
4. Conclusion
The second phase of Danjiangkou Dam is the largest heightening construction of water conservancy project in China so far, and it is difficult to ensure the normal operation and management of the hub during the construction period. However, due to the high attention paid to construction technology, the contradiction between operation management and construction is less considered, and some problems have not been paid enough attention, which will not only affect the operation management and efficiency of the hub, but also have a negative impact on the construction of the second phase project. In order to ensure the smooth construction of the project and the safe operation of the dam, the author thinks that the relationship between hub operation management and project construction should be deeply studied as soon as possible, practical and effective measures should be formulated, new management concepts and technologies should be introduced into the project construction, the construction management level should be improved, and both operation management and dam heightening construction should be given consideration, so as to ensure the normal operation management of the hub while ensuring the construction quality and progress.
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