032 | How It Works
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At maximum capacity, the lake on the upstream side of the dam can yield 219,700kg/m2 (45,000lb/ ft2) of force at its base.
Lake Mead
How It Works explores one of the world’s greatest engineering feats
into them and filling cavities with more grout. Chief engineer John Savage had decided it would be an arch-gravity dam, which combines the main features of two different types of dam: the arch part is a concave face that leans towards the water, deflecting some of the pressure onto the canyon walls, while the gravity part of the design is the enormous weight of the dam that thickens considerably from the top (13.7 metres/45 feet) to the bottom (201 metres/660 feet). This helps to resist the immense force that the Colorado River can generate with its 5.5 million-ton weight. To help dissipate the heat generated by all this concrete setting, around 950 kilometres (590 miles) of steel piping delivered water cooled by the dam’s dedicated ammonia refrigeration plant through the 230 concrete blocks that make up the structure. Without this active cooling system in place, all that concrete would still be setting today! Constructing the Hoover Dam would have been impossible with the Colorado River still flowing through Black Canyon. So, the builder endeavoured to divert the course of the river. Four tunnels with a combined length of over five kilometres (three miles) were dug into the canyon walls and around the dam site. The river was diverted into these tunnels by
Overflow from Lake Mead drains downstream via these inlets. They’ve been used only twice since the dam was built.
Spillway inlet
blocking its natural course with rubble as well as detonating a hole in a cofferdam – a temporary enclosure that stopped the river draining into the diversion tunnels. This was only performed for the two tunnels on the Arizona side of the canyon. The two drainage tunnels on the Nevada side were held in reserve for the higher waters in spring and summer.
Diverting the Colorado River
TECHNOLOGY
Hoover Dam structure
In the early-20th century, the lower region of the Colorado River was considered as a site for flood control and potential source of hydroelectric power for the growing demands of western US states. What would be known as the Hoover Dam was authorised by President Calvin Coolidge in 1928 and construction began by building conglomerate Six Companies in March 1931. At the time the Hoover Dam was the largest in the world requiring over 3.3 million cubic metres (118 million cubic feet) of concrete to build, including the power station. Before the dam could be built, foundations had to be laid and over 1.3 million cubic metres (48 million cubic feet) of loose rock and sediment were removed from the bottom of the Colorado River to reach stable bedrock. The foundation was reinforced with a grout curtain and the canyon walls were similarly stabilised by drilling holes up to 46 metres (150 feet) deep
It was one of the most ambitious projects in the world, but how was the Hoover Dam constructed?
Hoover Dam construction
“The Hoover Dam was the largest in WorldMags.net the world requiring over 3.3 million cubic metres of concrete to build”
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