Did you know about Hoover Dam? How it was built?

The Hoover Dam which was constructed eighty years past still stands strong and serves 

Image Credits: Google

the U.S and therefore the fields of irrigation control and power production even throughout torrential rainfall. You will not see dyke walls overflowing like this perpetrating destruction. Welcome to the engineering secrets of hoover dam. In this article, you are going to assume the role of dyke wall of dam designer engineer Mr. John L. Savage who constructs a huge dam in Arizona's Colorado stream. Mr. John Savage's surveying group zeroed in on the black canyon mountains alongside the Colorado stream. The justification is the mountains have a reasonable height and narrow gaps between them consenting to huge savings on construction material. However several strategic challenges were still ahead of the project's chief engineer. Let's begin with the look of a straight concrete wall of uniform breadth. The robust water pressure clearly causes the wall to deform and bend. You can observe that with this bending the outer fibers become elongated and therefore the inner fibers area unit compressed. This set of circumstances ends up in tension on the walls downstream facet and compression on its upstream facet. When tensile pressure is applied to concrete, it just develops cracks. Generally, popular buildings use steel bars to beat this issue as steel rods can endure a massive tensile load. However Mr. John Savage had a far simpler solution that doesn't require steel rods “The arch dam technology”. When curvature is given to a dam, it becomes an arch dam. This arch dam deforms underneath the water loading. Now if you compare this dam's biased shape with its original shape, you may notice that each of the upstream and downstream fibers area unit undergoing a length reduction which implies the whole dam body is going to be underneath. Compressive loading concrete will stand up to robust compression forces. This is the cool beauty of arch dam technology. However, if we tend to place the dam underneath service it still incorporates a sensible probability of falling due to the water pressure. We can solve this issue by increasing the dyke wall thickness bit by bit toward the base. This methodology can lower the dam wall's center of gravity. The lower the center of gravity, the greater object's stability. The design we tend to achieve just is called a gravity arch dam and this design will overcome the problems of tensile stress and stability. This cumulative design can even resist sheer forces. The water pressure diagram on the dam body isn't uniform but is triangular in form and increases toward the bottom. However, since the zone of the dam increases toward the bottom, the pressure at every cross section is nearly identical.

The next massive challenge Mr. John L. Savage faced was the height of the dam. The bigger the dam, the more water it holds. This is noticeably an advantage for electricity generation and flood control but is it potential to construct a dam that is identical in height to the mountain walls? First, we want to investigate the most flood discharge that may occur throughout the dam's lifetime depending on the regional downfall information and area structure. After constructing such a tall dam even during a torrential stream flow if the dam isn't obtaining crammed to its capacity then it's clearly been overdesigned. Moreover building a taller dam needs considerably additional materials drastically increasing its construction value. Therefore Mr. Savage carefully chooses a height that was value effective, meets the water demand of nearby cities, and conjointly also does flood control at the peak he selected 726 feet. The main part of this dam is currently complete. Now the foremost interesting part executing its structure is an arch-gravity dam that wants strong mountain walls to transfer the load.

Let's take a cross-section of the mountains. You'll see the rocks on the surface are weatherworn and relatively weak. Therefore the primary task throughout Hoover’s construction was to get rid of all those weatherworn rocks till solely the virgin ones remained. To reach the Virgin rocks the workmen drilled holes with jackhammers and blasted them with dynamite. After blasting athletic workmen were sent with ropes to clear loose rock from walls and therefore the excavated material was transferred away via trucks. This dam must have a robust joint with the sidewalls for this purpose they excavated the mountain in the form of an arch. Once more using dynamite explosion, the dam body takes shapes from these deep holes creating the mountain wall dam association extremely robust.

Now the successive massive question is whether the ground can bear the load of such a massive dam. Once excavating it's racial to succeed in a robust layer of soil called solid strata. To find the solid strata the workers used power shovels and excavated the bottom to a depth of an enormous 135 feet. They excavated the bottom within the same width because of the base breadth of the dam. One detail we tend to not mention is that before they began all this work they had to first divert the stream flow in another direction to try so they constructed temporary coffer dams and diversion tunnels. Now it is time for the concreting for these we tend should first prepare the formwork which is created from wood for the concreting. Once the formwork is done we'll begin running the concrete. However, the most issue here is that once cement reacts with water it produces heat. Considering the size of the project running all the concrete directly will produce a massive store of warmth which will lead to material expansion and thermal cracks within the concrete making the project a failure. To solve this issue the engineers smartly divided the whole dam space into a number of blocks just about fifty by fifty feet and poured concrete into every block one by one. These tiny quantities of concrete took abundant less time to cool down. Additionally, they embedded steel pipes into these blocks. The pipes carried cool water which controlled the temperature within the concrete and set it quickly and simply. Once the concrete hardened, they filled these steel pipes with a grout cement suspension. This method established even effective that the dyke wall hasn't shown any cracks.

Now let's explore the hoover dam's biggest application of electricity production. You might have determined four immense towers inside the dam's water body. In this area unit intake towers, many gates on the height of those towers regulate the water flow rate. The intake tower is then connected to these five-hundred-foot-long penstocks that carry water to the turbines to generate power. Mr. Savage designed a u-shaped power station at the bottom of the dam. Downstream water from the penstocks turns seventeen Francis sort vertical turbines that rotate a series of electrical generators. Each of those generators produces enough electricity to serve a hundred thousand individuals. Later this water is free through outlets downstream for irrigation purposes. The dyke wall then irrigates additional one hundred thousand acres of land. Interestingly the dam conjointly creates one of the biggest artificial lakes. Within the world reservoir, this immense water storage facility helps groundwater recharge so increasing the water level in close wells. The next obvious application of the hoover dam is control just in case of flood or heavy rain falls. The barrage stores the rainwater in the reservoir and prevents it be due threatening the lives and structures in the downstream space.

Now let's think about a little design challenge. What if the dam overflows? It can simply damage the structures built downstream. To resolve this potential drawback, they created passageways referred to as spillways on either side of the dam upstream in order that water can be spilled downstream. These spill area units were placed twenty-seven feet below the top of the dam. If water reaches that level, it tends to start flowing into spillways. You just will truly walk inside the dyke wall body because many tunnels are hidden within the dam body. They have to construct these tunnels because of an easy development with which we're all acquainted water oozing. A liquid under pressure continuously desires to escape through the porous material. Here the water flows through the soil below the dam body. This flow creates a high uplift pressure on the base of the dam considerably reducing its stability. This is why Mr. Savage designed a gallery a tunnel that collects all oozing water from the dam body and base. This action reduces the uplift pressure considerably the collected water is then discharged safely the galleries conjointly provide passageways for a leak or crack. We hope you enjoyed learning all about this engineering effort.