Scientific and technological achievements of Longtan Hydropower Station

The Hongshui River Longtan Hydropower Station has an initial water storage level of 375 meters, an installed capacity of 4.2 million kilowatts, a maximum dam height of 192 meters, and a dam body concrete of 5.322 million cubic meters; in the later stage, the normal water storage level is 400 meters, with an installed capacity of 540 kilowatts. Thousands of kilowatts, the maximum dam height is 216.5 meters, and the concrete pouring volume of the dam body is about 6.8 million cubic meters. The preliminary design and approval of the hub layout plan is: normal concrete gravity dam and water release buildings are arranged in the riverbed dam section; the power plant is the powerhouse behind the riverbed dam (installed with 5 units) and the left bank underground powerhouse (installed with 4 units); the navigation buildings are arranged in Right bank. This plan is referred to as the "5 4" plan. On the basis of the initial approved plan, the Central South Survey and Design Institute further studied the hub layout, dam shape optimization, and new technology of roller compacted concrete dam construction. This will not only save engineering work, but also help generate electricity one year earlier than the original design plan. For this reason, "Research on Structural Design and Construction Methods of Longtan RCC Gravity Dam" was included in the fourth topic of the "Eighth Five-Year Plan" national key scientific and technological research project "Research on Key Technologies for High Dam Construction". The research goal of this topic is: combined with the design of Longtan Hydropower Station, summarize a new set of 150-meter-level RCC dam construction technology suitable for my country's national conditions.

Longtan Hydropower Station combines scientific and technological research with design optimization. The key scientific and technological achievements it has achieved include the following aspects:

(1) Optimization of hub layout

On the basis of the preliminary design approval plan, the "5 4" plan was compared, and the "0 9" plan (full underground powerhouse plan) was focused on supplementary research, creating more favorable conditions for the rapid construction of the RCC dam. At the same time, the stability and treatment measures of the creeping rock mass at the left dam head of the scheme and the high slope of the water inlet, the stability of the surrounding rock of the underground cavern group, and the construction progress of the underground engineering were also analyzed. The final design recommends the "O 9" plan. The advantages of this plan are: (1) The "0 9" plan has no factory building behind the dam, no water inlet on the dam, and no steel pipes in the dam, which simplifies the dam structure and reduces the number of factory and dam costs. The interference of construction has increased the application scope of the dam body's RCC, which is conducive to the rapid construction of RCC, allowing the entire civil engineering project to generate electricity one year in advance. (2) The Hongshui River has a long flood season and a large flow. It is difficult to overcome the flood and discharge and dissipate energy during the construction period. Eliminating the post-dam powerhouse not only simplifies diversion measures, but also makes the layout of permanent water release structures more flexible. (3) The "0 9" plan has no factory buildings behind the dam and no steel pipes in the dam, which enhances the rigidity of the upper dam body and helps to improve the stress of the dam body, especially the stress of the dam body under earthquake action. (4) This plan has only one factory building, which is convenient for operation, management and maintenance, and facilitates the heightening of the dam body in the second phase and the normal water storage level.

The "0 9" plan was reviewed and approved at the Longtan Hydropower Station plant layout plan review meeting held in December 1992.

(2) Experimental research on material properties

In order to understand the properties of roller compacted concrete, especially whether the layer shear resistance parameters can meet the requirements for building a 200-meter high roller compacted concrete gravity dam , carried out the optimization of concrete mix proportions, the development of retarding water-reducing admixtures and large-scale on-site rolling tests. From October 1990 to December 1992, we simulated the construction conditions of normal temperature conditions and high temperature conditions on rocky beach land with similar climatic conditions and basically the same raw materials, and conducted 3 large-scale construction projects under 10 working conditions. For large-scale on-site rolling compaction tests and on-site in-situ shear resistance testing, the total amount of roller-compacted concrete reached 819 meters and there were 284 in-situ shear resistance test blocks. Through a large amount of test data analysis and research, we have basically clarified the main influencing factors that affect the material properties of RCC, especially the layer shear strength, such as environmental conditions, especially temperature and evaporation, the amount of cementitious materials, and the interlayer pouring interval time. and treatment measures, etc. As long as these main factors are properly controlled, the construction requirements for Longtan's 200-meter high roller compaction concrete upper gravity dam can be met.

(3) Optimization research on the shape and structure of the dam

Based on the material properties of RCC in field tests, the shape and structure of the dam were optimized. After research, The following major measures have been taken: (1) The dam is made of gel-rich RCC material, and the full height is poured with RCC on a 6-meter-thick cushion; (2) A special reinforced concrete anti-seepage panel is installed on the upstream face of the dam ( 1 meter thick); (3) Under the condition of ensuring the safety of the dam, the body shape design pursues the minimum concrete engineering volume, and the cross-sectional size does not need to be specially enlarged compared with the normal concrete dam; (4) When calculating the dam base surface pressure, the pumping is included To achieve the drainage and pressure reduction effect, vertical and horizontal drainage corridors are set within the normal concrete cushion of the dam foundation; (5) Simplify the dam structure as much as possible and expand the scope of using roller compacted concrete for the dam body.

The optimized Longtan roller compacted concrete upper gravity dam section has a bottom width of 168.5 meters, a maximum dam height of 216.5 meters, and a width-to-height ratio of 0.78. The shape and structure finally adopted in the optimized design can meet the design requirements for the stability and stress of the dam foundation surface and any calculated section within the dam. It has exceeded the 150-meter height of RCC originally planned for the "Eighth Five-Year Plan", making the RCC height Reaching 200 meters, it is currently the highest in the world. The dam uses roller compacted concrete with a cubic meter volume of 3.35 million cubic meters, which is 63% of the original designed initial dam concrete volume of 5.322 million cubic meters.

After several years of scientific and technological research and design optimization, the Longtan Project has been able to save 350,000 cubic meters of concrete in the dam body and more than 150 cubic meters of earth and rockwork compared with the original plan. 10,000 cubic meters, which can save more than 200 million yuan.

Longtan Hydropower Project won the FIDIC Centennial Engineering Project Award, pushing Longtan Hydropower Project onto a world-class engineering platform. In 2007, Longtan Dam was awarded the Roller Compacted Concrete Milestone Project Award by the International Commission on Dams. "Key Technologies and Engineering Practice in the Transition Process of Hydropower Stations", "Development and Application of New Flood Discharge and Energy Dissipation Technology in High Dam Projects", "Key Technologies for 200-meter High RCC Gravity Dam", "Intelligent Feedback Analysis Method of Rock Mechanics and Its Engineering Application" won the second prize of the National Science and Technology Progress Award in 2008, 2009 and 2010 respectively.