In the previous article we have seen, which location is suitable for the dam. what are the engineering concepts behind building hoover dam, the features of arch dam technology, why did they choose gravity arch dam technology, and how do they define the height of the dam? The important thing, I would like to mention that before the engineers began the construction work, they had to first divert the river flow in another direction. To do so, they constructed temporary cofferdams and diversion tunnels as shown in fig 1.
Many people can think that overflow can easily damage the structures constructed downstream. To solve this potential problem, engineers constructed passageways, called ‘spillways’ on either side of the dam upstream so that water can be spilled downstream. These spillways (refer fig 2) are located 27 feet below the top of the dam. If water reaches that level, it starts flowing into spillways.
Do you know that you can actually walk inside the hoover dam body? Several tunnels are hidden inside the dam body. They constructed these tunnels (refer fig 3a) because of a simple phenomenon with which you might be familiar - water seepage. A liquid under pressure always wants to escape through porous material. Here the water molecules flow through the soil below the dam body due to the seepage effect (refer fig 3b). The issue is that this flow generates a high uplift pressure on the base of the dam, reducing its stability. This is why Mr. Savage designed a gallery, a tunnel that collects all seepage water from the dam body and base. This action reduces the uplift pressure considerably. The collected water is then discharged safely. These galleries also provide passageways for leak or crack inspections.
Such detailed engineering plans with a future-focused vision are the reason why the Hoover Dam is still standing strong and serving the nation.
Thanks for reading!