Influence of Hoover Dam on Natural Environment of Colorado River Estuary

1 The water quantity decreases, and the irrigation water source in the estuary area decreases.

Sediments were intercepted and the estuary delta contracted.

3. Sea water invasion, land salinization in the estuary area.

4 sediment interception, the land in the estuary area is reduced.

Hoover Dam is a key project for the comprehensive development of Colorado river water resources in the United States. It is located in the Black Canyon at the junction of Nevada and Arizona, and has comprehensive benefits such as flood control, irrigation, power generation, shipping and water supply. The dam is a concrete gravity arch dam with a height of 221.4m. The reservoir formed by the dam is called Lake Mead with a total storage capacity of 34.85 billion cubic meters. The installed capacity of the hydropower station was originally 6.5438+0.34 million kilowatts, but now it has been expanded to 2.08 million kilowatts, with a planned capacity of 2.452 million kilowatts. Construction started in April, 193 1, completed in March, 1936, and the first power generation was officially started in June.

Overlooking the Hoover Dam, it is located in northwest Arizona, on Interstate 93, at the junction of Nevada and northwest Arizona. Due to the one-hour time difference between Arizona and Nevada, there is a clock at each end of the dam to facilitate passengers to time. Depart from Las Vegas and drive southeast for about 40 kilometers. This project is huge and will play a great role in the development of industry and agriculture. Therefore, it occupies an important position in the ranks of water conservancy projects in the world. The construction of Hoover Dam cost a lot of money and mobilized a lot of manpower. It was completed and put into use on 1936. This is an arch gravity artificial concrete dam. The dam is 220m high, 200m wide at the bottom,14m wide at the top and 377m long. Such a huge dam is rare in the world.

Hoover Dam is an arch gravity artificial concrete dam and a world-famous water conservancy project. The Colorado River under the dam used to be the deepest and fastest river in America, but now it walks slowly like a tame beast.

Hub layout

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The main buildings of the project include barrage, diversion tunnel, spillway tunnel and power station.

Schematic diagram of dam overflow

The barrage is a concrete gravity arch dam with a dam height of 22 1.4m, a dam crest length of 379m, a dam crest width of 13.6m, a maximum dam bottom width of 202m, a dam crest radius of 152m, a central angle of 138, and a dam concrete pouring volume of 2.485 million cubic meters.

There are two diversion tunnels on the left and right banks, with a diameter of 15.25m, a total length of 4860m and a diversion flow of 5,670m3/s. The two tunnels on the left bank were first built in 1932+065438+ 10.

There are 1 spillway tunnels on the left and right banks, and the water intake is controlled by four 4.9m×30.5m radial gates. The spillway tunnel is reconstructed from the second half of the diversion tunnel, with a diameter of 15.2m, concrete lining, a length of 67 1m, a maximum flow of 53.4 m3/s, and a total spillway discharge capacity of11400m3/s. ..

The other two diversion tunnels were transformed into power generation diversion tunnels and used as auxiliary flood discharge tunnels. The auxiliary spillway tunnel is equipped with six 3.96m steel pipes at the end of the diversion tunnel, with a total discharge of 2577 cubic meters per second.

There is a shore-based powerhouse on the left and right banks, with a length of 198m, and the top of the powerhouse is 45.7m higher than the normal tailrace level. The two power generation diversion tunnels on the left and right banks (each with 1 diversion tunnel) are divided into eight pressure pipes, one of which is divided into two pressure pipes, and the *** 17 pressure pipe supplies water to the 17 turbine. The installed capacity of the power station reaches 2.08 million kilowatts, of which 13 1 30,000 kilowatts, 2 1 27,000 kilowatts,168,500 kilowatts,16150,000 kilowatts.

Dam engineering

Hoover Dam is built in a deep and narrow canyon, and the bedrock of the dam foundation is hard andesite and breccia. Cement grouting curtain and drainage holes are set in dam foundation to reinforce the upstream shear zone by grouting. The dam construction adopts the columnar pouring method, which is divided into 230 columnar blocks, the upstream block is 5m× 18m, the downstream block is 7m×9m, and the pouring layer thickness is1.5m. This dam is the first high dam with buried water pipes for cooling in China. * * * Layout 6×3m? And 4×3m? Mixing building 1 seat, with a production capacity of 7560 cubic meters/day; There are 5 23t translational cable cranes and 6 1 13t cable cranes, and 6 cubic meters of hanging tanks are used to pour concrete.

The layout of the Hoover Dam project is very compact. The excavation of diversion tunnel was completed in May 193 1 year, and the lining was completed in autumn 1932. 1June 1933, concrete pouring began.1March 1935, 2.48 million cubic meters of concrete was poured, which lasted 2 1 month, and the gravity arch dam with a height of 22 1m was poured to the top of the dam. At the same time, the water intake building, pressure pipeline, power station, spillway, spillway tunnel and transmission line are all working in parallel.

The volume of concrete pouring in this project is 3.36 million cubic meters, the daily maximum pouring strength of concrete is 7,520 cubic meters, the monthly maximum pouring strength is 6.5438+0.98 million cubic meters, and the monthly average pouring strength is 6.5438+0.65438+0.5 million cubic meters.

Engineering characteristics

Creative development of mass concrete high dam construction technology, some technologies have continued to this day. In terms of concrete dam construction machinery and technology, such measures as dividing the dam into 230 vertical columnar blocks and burying cooling water pipes to solve the heat dissipation problem of mass concrete pouring have become successful examples in mass concrete engineering, which has had a great impact on the formation and development of concrete dam construction technology in the world.

During the flood discharge operation of Hoover Dam 194 1 year, serious cavitation damage occurred, indicating that there are still some problems in the hydraulic design and construction technology of flood discharge for large-diameter tunnels with high head. The Francis turbine also had cavitation problems, and later a new stainless steel turbine was installed.

Engineering benefit

Hoover dam has played a great role in flood control, irrigation, urban and industrial water supply, hydropower generation, shipping and so on:

Lake Mead Reservoir formed by Hoover Dam has a regulating capacity of 65.438+09.6 billion cubic meters and a flood control capacity of 65.438+065.438+07 billion cubic meters, which can completely control the flood above the dam site. The reservoir prevented frequent floods downstream, which reduced the flood flow of the Colorado River from 5670 cubic meters per second to 1 130 cubic meters per second, and the extraordinary flood peak from 8500 cubic meters per second to 2 120 cubic meters per second. For example, the flood flow of 194 1, 1952 and 1958 is 2920 ~ 3450 m3/s, and the flood discharged from the reservoir is below 1000 m3/s after flood dispatching. After the completion of the dam, 700,000 hectares of land in the desert areas of California and Arizona have been guaranteed by reliable irrigation water sources. Objective The irrigation area can produce more than $6,543.8 billion of agricultural products every year. It can provide domestic water for 32 million families of five every year. In the semi-arid area of southern California, the annual precipitation is only 380mm, which is far from meeting the water demand in this area. Therefore, in 1974,13.2 billion cubic meters of water was pumped from Lake Mead, which was supplied to 25 towns in Southern California and industrial and mining enterprises with 100 square kilometers, including Los Angeles100 million people. The length of the reservoir is 177km, which can be used by ships and yachts of all sizes, changing the face that the dam was basically navigable before its completion. This reservoir has beautiful scenery and is a famous tourist attraction.

work progress

The Hoover Dam started in 193 1 March, 2008 1 1. The chief engineer is Frank Crowe, and the dam is funded by the government.

Hoover dam

Help, so he must finish it within the time limit stipulated by the government, or his company will face a huge fine of $3,000 a day. Before they build the dam, they must first open a road to the canyon to transport materials. Because during the Great Depression, the number of unemployed people increased greatly, which provided a considerable amount of cheap labor for dam construction.

Before the dam is built, the Colorado River must be diverted, but there are cliffs on both sides of the river, so the only way is to drill and blast on both sides of the canyon and open four diversion tunnels. However, the living and working environment of the workers who opened the shunt tunnel went from bad to worse, which made many workers more and more dissatisfied with Goyle and even planned a strike. On August 7th, the workers went on strike. At that time, a large number of unemployed people were qualified to replace them. Therefore, the workers took great risks and even lost their jobs. Gore chose to suppress the strikers, fire them, and then recruit again. 1932 Hanoi flows into the tunnel for the first time, the diversion project is successful, and the dam is formally built. The remaining project is just to build a dam with concrete. The deadline given by the government is four and a half years. Although there is a lot of time, Goyle wants to finish it early in order to get a big bonus. 1933 A total of one million cubic yards of concrete was poured. 1935, the dam was completed two years ahead of schedule, and Goyle also received a bonus. Hoover Dam killed 1 12 workers.