The beautiful Hoover Dam, built 80 years ago, is still functional and serves the United States. The fields of irrigation flood control and power production. Even during a torrential rainfall you won’t see hoover dam overflowing causing destruction. Welcome to the Hoover Dam’s engineering secrets. Let’s see the interesting facts about The Hoover Dam.
Interesting facts about The Hoover Dam
A massive dam was designed and built in the Colorado River in Arizona by engineer Mr. John Savage. Mr John savage’s surveying team zeroed in on the black canyon mountains beside the colorado river. The reason the mountains have a decent height and narrow gaps between them allowing for huge savings on construction materials.
However many design challenges were still ahead of the project’s chief engineer. Let’s start with the design of a straight concrete wall of uniform width. The wall deforms and bends naturally due to the high water pressure. Due to this bending the outer fibers become elongated and the inner fibers are compressed.
This scenario results in tension on the walls downstream side and compression on its upstream side. Concrete is easily cracked when subjected to tensile tension. Steel bars are typically used in modern constructions to solve this problem because they are easily able to support heavy tensile loads. However Mr. John savage had a much simpler solution one that does not require steel rods the arch dam technology. When you give curvature to a dam it becomes an archdam deforms under the water loading.
Now if you compare this dam’s deformed shape with its original shape you’ll notice that both the upstream and downstream fibers are undergoing a length reduction. Which means the whole damn body will be under compressive loading. Concrete can withstand strong compression forces. This is the simple beauty of archdam technology. However if we put the dam under service it still has a good chance of toppling due to the water pressure. We can solve this issue by increasing the dam’s width gradually toward the base.
The approach will lower the dam body’s center of gravity. The lower the center of gravity the higher an object’s stability. The design we achieved just now is called a gravity arch dam and this design can overcome the issues of tensile stress and stability. Additionally, this design’s expanding width can withstand shear stresses.
The water pressure diagram on the dam body is not uniform but is triangular in shape and increases toward the base. The shear stress value for each cross section is essentially the same, despite the fact that the area of the dam grows towards the base.
The next big challenge savage faced was the height of the dam. The higher the dam the greater its water storage capacity. This is obviously an advantage for electricity generation and flood control. But can a dam that matches the height of the mountain walls be built?
First we need to analyze the maximum flood discharge that can occur during the dam’s lifespan which depends on the regional rainfall data and catchment area. If the dam is not filling to capacity after being built to such a height, even amid a torrential river flow, it has undoubtedly been overdesigned. Moreover building a taller dam requires significantly more materials drastically increasing its construction cost. As a result, Mr. Savage chose a height that was both cost-effective and met the water needs of adjacent cities while also acting as a flood control measure. The height he chose was 726 feet. The main design part of this dam is now complete. Putting its construction into action is now the most exciting aspect.
Construction Of Hoover Dam
Putting its construction into action is now the most exciting aspect. It needs sturdy mountain walls to transfer the weight because it is an arch-gravity dam. If we take a cross-section of the mountains you can see the rocks on the surface are weathered and quite weak.
Thus, clearing away all of those weathered rocks until just the fresh ones left was the initial chore during the hoover’s construction. The construction workers used jackhammers to dig holes and explosives to burst through the virgin rocks. After blasting acrobatic workmen were sent with ropes to clear loose rock from walls and the excavated material was transferred away via trucks.
This dam should have a strong joint with the sidewalls for this purpose. They once more used dynamite explosions to create an arch-shaped excavation in the mountain wall. The dam body takes form from these deep holes making the mountain wall dam connection really strong.
Now the next big question is how the ground will bear the weight of such a massive dam. When excavating it is crucial to reach a strong layer of soil called hard strata. To find the hard strata the workers used power shovels and excavated the riverbed till a depth of a whopping 135 feet. They dug a riverbed that was the same width as the dam’s base. One detail we didn’t mention yet is that before they began all this work they had to first divert the river flow in another direction. To do so they constructed temporary coffer dams and diversion tunnels.
However the main issue here is that when cement reacts with water it produces heat. Given the size of the project, pouring all the concrete at once would result in a huge buildup of heat, which would cause the concrete to expand and develop thermal cracks, rendering the project a failure. Here is a new development in construction to address this problem. The engineers cleverly divided the entire dam area into a number of blocks each approximately 50 by 50 feet and poured concrete into each block mold work one by one. These modest amounts of concrete cooled more faster.
In addition they embedded two inch diameter steel pipes into these blocks. The pipelines transported cool water, which helped to regulate the concrete’s temperature and swiftly and readily set it. Workers filled these steel pipes with a grout cement slurry after the concrete had cured. Since this method was so successful, the Hoover Dam has not yet showed any cracks.
Hoover dam’s biggest application : Electricity production
Let’s now examine the specifics of the largest use of the Hoover Dam electricity production. You might have observed four huge towers inside the dam’s water body. These are intake towers. Several gates along the height of these towers regulate water flow rate. The intake tower is then connected to these 500 foot long pen stocks that carry water to the turbines. To generate power. A u-shaped power plant, designed by Mr. Savage, is located downstream at the base of the dam. Water from the pen stocks turns 17 francis type vertical turbines which rotate a series of electric generators. Each of these generators produces enough electricity to serve 100 000 people.
Later, this water is released for irrigation purposes through outlets further downstream. The hoover dam irrigates more than one million acres of land. Interestingly the dam also creates one of the largest man-made lakes in the world. Lake mead this huge water storage facility helps groundwater recharge. Thus increasing the water level in nearby wells.
The next obvious application of hoover dam is flood control. In case of flood or heavy rains the dam stores the water in the reservoir and prevents its flow from threatening the lives and structures in the downstream area. Now let’s consider a small design challenge what if the dam overflows. It can easily damage the structures constructed downstream. On either side of the dam upstream, they built channels known as spillways to address this possible issue. So that water can be spilled downstream.
These spills are located 27 feet below the top of the dam. If water reaches that level it starts flowing into spillways. You can actually walk inside the body of the Hoover Dam, did you know that? The body of the dam contains a number of tunnels. They have to construct these tunnels because of a simple phenomenon with which we’re all familiar water seepage.
A pressurised liquid will always try to escape via porous material. Here, the seepage effect causes water molecules to move through the earth beneath the dam body. The issue is that this flow generates a high uplift pressure on the base of the dam drastically reducing its stability. For this reason, Mr. Savage created a gallery. a tunnel that drains the dam’s body and base of all seepage water. This action reduces the uplift pressure considerably the collected water is then discharged safely the galleries also provide passageways for leak or crack.
Inspections such detailed engineering plants with a future focused vision are the reason why the hoover dam is still standing strong and serving the nation. We hope you enjoyed learning all about this engineering feat. Before the article ends we would like to pay homage to all 96 workers who sacrificed their lives to make this gigantic dam a reality.