Three Gorges Dam is located in Yichang City, Hubei Province, upstream of the Yangtze River . It is the world's largest water conservancy hub and can be regarded as a benchmark work in China's water conservancy industry. However, since the start of construction in 1994, the debate on dam-centered has not been interrupted, and the safety of the hub has been questioned many times.
Especially since 2011, Sanxia Reservoir stored water for the first time to 175m, with a total storage capacity of 39.3 billion m³, just like a "big water basin" hanging above the head of Jingjiang , and the safety of the dam is also highly valued. Once there is a problem with the Three Gorges Dam, the downstream Jingjiang Dike will be the first to be affected, and the consequences will be unimaginable.
Three Gorges Dam: It was once listed as a "target". What is the security?
The Three Gorges Dam is a flood control tool for the Yangtze River. The water storage volume under normal water levels accounts for 4% of the Yangtze River's annual runoff, and the water storage area reaches 1,084 square kilometers. Ensuring the water storage safety of hub dams has always been the top priority.
Objectively speaking, the factors that threaten the safety of the Three Gorges Dam are divided into two aspects. One is natural threats, such as earthquakes, flood impacts, weathering and erosion, etc.; the other is human threats, such as explosives, missiles, and even nuclear bombs, attacks. In terms of the degree of harm, the first thing to be vigilant is human threats, and the ammunition is extremely destructive, which may cause hidden dangers to the dam's flood control function.
In 2004, criminals listed the Three Gorges Dam as a "military strike target" and tried every means to spy on the relevant situation and obtain intelligence information about the dam.
For example, in April of that year, three suspicious "tourists" were arrested by the guards of Sanxia Reservoir Area . The three people not only carried large-scale fine maps, but also equipped with satellite positioning system , pistols and other equipment. In the seized camera, the guard also found scene photos around the dam. This information should not be underestimated and may provide a basis for the end guidance of precisely guided weapons.
Our country has long had solutions to illegal activities with ulterior motives. From 1959 to 1988 before construction started, the engineering department conducted scenario simulations on the chemical explosion hits and nuclear bomb hits of the Three Gorges Dam, and conducted more than 200 simulation tests on the dam collapse of 400m and 1000m in the full-storey state. Finally, the expert team came up with the most secure design plan to ensure the safety of the Yangtze River for a century.
After storing water, what is the safety of the Three Gorges Dam? In a nutshell: relies on the structural strength of the dam itself and can fully withstand the attacks of conventional weapons such as ! Being able to achieve this level is closely related to three aspects.
is the first choice for the dam type. The dam type of the Three Gorges Dam is the most stable and resistant concrete gravity dam . The dam body has a triangular section, and the height of the dam is, the width of the bottom of the dam is. The base of the dam is 124m wide, the top width is 15m wide, the axis of the river dam is 2309.47m long, the dam is 181m high, and the volume is huge. The concrete strength ranks first in the world, and the dam body is extremely stable.
followed by a safe engineering design. In order to ensure the safety of the dam, a variety of insurance measures have been taken in the engineering design, such as: appropriately lowering the elevation of the dam foundation, setting up cogs at the dam heels to increase stability; setting up anchor bars and contact grouting systems between the rock slope and the concrete of the factory building to make the slope and the factory building closely abut and increase the anti-slip capacity; controlling blasting throughout the process to ensure that the construction process does not affect the integrity of the bedrock body.
In addition, the geological safety of the dam site and upstream has also been taken into consideration. There is no unstable slope that threatens the hub in the 26km of the upstream river section near the dam, the geological structure is stable, and earthquakes are not prone to occur in the core area, and collapses and landslides will not affect the safety of the project.
finally has higher than the standard construction quality. The Three Gorges Project took 12 years to complete, and the comprehensive performance of the materials exceeded the national standards. Take the freezing resistance of concrete as an example: The Three Gorges Dam is not a cold area and the freezing resistance of concrete is not high. However, in order to improve durability (service life), the project still uses high-grade freezing resistance concrete. The internal concrete label is F100, the foundation concrete is F150, and the other parts are F250, which is far higher than the actual freezing resistance requirements.
Overall, the Three Gorges Dam is like a copper wall made of reinforced concrete. The hub is large in scale and has a high structural strength. It can fully bear the heavy responsibility of water storage and water retention, and there is no need to worry about safety.
Will the Yangtze River flood pose a threat to the Three Gorges Dam?
As my country's national strength continues to improve, the threat of human factors is far lower than expected. Under my country's strong nuclear deterrence, the possibility of the dam being attacked by missiles and nuclear bombs is almost zero, which is undoubtedly true.
Some netizens may be worried: Although the probability of human threats is very low, natural threats occur almost every year. In recent years, the main stream of the Yangtze River has frequently experienced large flow floods. Will the surging river water pose a challenge to the safety of the dam?
There is no need to worry about the threat of Yangtze River floods, because the Three Gorges Dam itself is designed according to the flood control standards once in 1,000. After adding 10% verification, it can withstand the super flood once in 10,000 . According to the data, the designed water barrier level of the Three Gorges Reservoir of is 175m, which can cope with 98,000 m³/s flow shocks; the checked water barrier level is 180.4m, which can cope with a maximum flow shock of 124,000 m³/s flow shocks of .
What exactly does this mean? We can compare the Yangtze River floods in history. Hydrological data shows that the largest flood recorded in the Yangtze River occurred in 1870. According to hydrological evidence, the peak flood flow at that time reached .105 million m³/s, which indeed exceeded the designed water barrier flow of the Three Gorges Dam, but it was still lower than the checked water barrier flow.
In 1954 and 1998, there were two major floods in the Yangtze River Basin, but the peak flow was much smaller. According to hydrological monitoring , the peak flow of the former in the Yichang section is 66,800 m³/s, while the peak flow of the latter is 63,300 m³/s, both within the designed water barrier flow of the Three Gorges Dam.
In fact, the scale of floods broke out in the upper reaches of the Yangtze River in 2010 and 2012 was larger, with the maximum inflow of 7~71,200 m³/s, but the economic losses caused were minimal. The reason is that the flood regulation and storage of the Three Gorges Dam played a role. After flood storage and peak reduction, the outflow of the Three Gorges Dam dropped to 40,000 m³/s. Even though there were many dangerous shoals in Jingjiang, it was still safe to survive the flood season and no flood disasters occurred.
Since the completion of the Three Gorges Dam, the Yangtze River flood control has had a "supernatural needle". Jingjiang's safe flood transportation standards have been raised from the original one-in-one 10 to 20 years to once in 100 years. Then, through the combined use of and Three Gorges Reservoir in Jingjiang Flood Diversion Zone, it can completely withstand once in a thousand years of floods.
Jingjiang River Trend Chart
Following the above conclusion: The once-in-a-thousand-year Yangtze River flood will not pose a threat to the Three Gorges Dam. As for the once-in-a-thousand-year flood, there has never been a relevant record so far.
The Three Gorges Dam has been storing water for nearly 20 years, why has it become stronger and stronger?
The Three Gorges Dam is not only not afraid of the impact and immersion of the Yangtze River flood, but will become more and more "solid" as time goes by.
Actual tests on the strength of the dam body show that the initial design value of the compressive resistance of the Three Gorges Dam concrete was 25MPa. By 2020, this indicator had risen to 43MPa, increasing 72% , which shows that the dam's compressive resistance is getting stronger and stronger.
Why is the longer the water storage time, the stronger the river dam?
First of all, in terms of waterproofing, the quality of concrete has been strengthened. By reducing the water consumption, adopting low water glue ratio, controlling construction vibration and maintenance measures, makes the internal concrete anti-seepage level greater than W8 and other levels greater than W10, so the dam body has good compactness.
Secondly, concrete will undergo a condensation and hardening reaction after pouring. The longer the time, the more cement it hardens and the stronger the overall compressive resistance. Therefore, the Three Gorges Dam is not only not afraid of long-term immersion, but will become stronger and stronger within 100 years.
How many years does the operating life of the dam have in terms of the properties of steel bars and concrete? According to experts, judging from the test results, "the concrete of the dam will not have any problems for at least 500 years. The conclusion of
does have some basis.According to the construction standards of the Three Gorges Dam structural concrete, the water-gluing ratio is less than 0.45. The carbonization experiment measured that the maximum carbonization depth in 28 days was only 1.26cm, which is equivalent to the carbonization depth in the natural environment for 50 years. The thickness of the protective layer of structural concrete is greater than 6cm, and to achieve the thickness of the protective layer of steel bars, the natural carbonization time must be at least 500 years.
summary
The Three Gorges Dam is the largest and most comprehensive dam in the world, and it is also the most solid and safest dam in China. Today, the Three Gorges Reservoir Area has also become an emerging tourist attraction in the Yangtze River. The reservoir of more than 600 kilometers is becoming the ecological core of the Yangtze River. The scene of fish and shrimps flocking, green water and green mountains are emerging.
The Three Gorges Dam plays an irreplaceable role in flood control, shipping, power generation, ecology, water supply, etc. of the Yangtze River. Under strict quality inspection and comprehensive protection, this century-old project will surely create greater wealth for the descendants of China.
