FYFD

Tag: civil engineering

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    Inside the LA Aquaduct

    In the early twentieth century, Los Angeles had capital and political willpower, but not water. So it built an engineering marvel, the LA Aquaduct, to guide water from the Sierra Nevadas down to the growing city. Grady gets into the literal (and figurative) ups and downs of the project in this Practical Engineering video.

    Although the engineering prowess of the aquaduct system is impressive, as Grady points out, the LA Aquaduct’s story is much more complicated than the engineering needed to move water between two points. It’s a story where greed, corruption, politics, cultural impact, environment effects, and climate change all intersect. (Video and image credit: Practical Engineering)

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    Fixing Mosul Dam

    Keeping the water in a reservoir is an obvious challenge for any dam. But for Iraq’s Mosul Dam, it’s especially challenging because the dam was built on a foundation of gypsum, a highly water-soluble mineral. Since it was built, Mosul Dam’s water has been eating away at the underlying bedrock, making sinkholes, forcing gaps, and generally working its way out. That, obviously, creates a huge risk for dam failure and massive downstream flooding.

    To get the dam stabilized–at least to a point where Iraqi engineers could keep up with filling the holes as they form–took a massive international engineering project, carried out in the shadow of armed conflict. (Video and image credit: Practical Engineering)

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    The Teton Dam Failure

    Engineering failures always leave us with lessons learned. The failure of Teton Dam in 1976 triggered an overhaul in how we manage dam construction and regulation. As Grady describes in this Practical Engineering video, the earthen dam was built with fundamental flaws that allowed water to carve pathways beneath and through the sediment meant to hold it. Although the dam cost $100 million to build, its failure cost the federal government over three times that in claims. (Video and image credit: Practical Engineering)

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    Why Unpaved Roads Washboard

    As anyone who has regularly traveled unpaved roads knows, they have a tendency to develop regularly spaced corrugations, otherwise known as washboarding. In addition to shaking cars and passengers, these uneven surfaces make cars harder to control, sicne the wheels can lose contact with the ground entirely at times.

    Unfortunately, this phenomenon is fairly unavoidable. Once you have a wheel moving across a granular surface above a critical speed, you get these self-reinforcing patterns. It’s similar to the way that tidal ripples and sand dunes form, and it’s how you get moguls on a ski run, too!

    Although they’re somewhat inevitable, as Grady describes, engineers are hard at work figuring out how to keep them from forming too quickly. (Video and image credit: Practical Engineering; research credit: N. Taberlet et al. and I. Hewitt et al.)

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    Breaking a Dam to Save It

    The concrete that makes up so much of our world is usually local in origin. To keep costs low, engineers use locally-sourced ingredients to make it. But not all ingredients perform the same.

    In the decades since concrete’s widespread adoption, engineers have discovered that some components in the concrete are prone to chemical reactions that cause the concrete to expand over time. For big infrastructure projects like a mid-twentieth century dam, this sparks a conundrum: how can we deal with expanding concrete without losing out on years of the project’s planned lifetime?

    To find out, see what Grady learned about the Tennessee Valley Authority’s clever method for relieving a dam’s stress. (Video and image credit: Practical Engineering)

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    Testing Structures Against Hurricane Storm Surge

    When hurricanes hit coasts, they bring with them incredible storm surge, which puts buildings right in the middle of ocean waves. To understand how to better protect against those conditions, engineers use facilities like the Directional Wave Basin to create smaller-scale versions of hurricanes. In this Practical Engineering video, Grady visited during a test that compared two identical one-third-scale houses subjected to the same storm conditions–except that one house had an additional foot (3ft at real-scale) of elevation. The results are pretty spectacular.

    This isn’t a short video, but it’s well-worth a watch. I think Grady does a great job of explaining why engineers need (admittedly) expensive facilities like this one to help guide both engineering and regulatory decisions. (Video and image credit: Practical Engineering)

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    Connecting Canals

    Before the rise of railroads, canals provided critical commercial shipping infrastructure for many locations worldwide. But connecting canals at different elevations required locks–sometimes a whole series of them–as in the case of Scotland’s Union Canal and the Forth and Clyde Canal. In the canals’ heyday, navigating the 11 locks between them took the better part of a day–one of many reasons that canals fell out of use over time.

    When Scotland decided to reconnect the canals in the 1990s, they picked a very different solution for this elevation challenge: the Falkirk Wheel. Grady walks us through the clever engineering of this impressive piece of infrastructure in this Practical Engineering video. (Video and image credit: Practical Engineering)

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    How the Edenville Dam Failed

    Back in May 2020, the Edenville Dam in Michigan failed dramatically, releasing flood waters that destroyed a downstream dam and caused millions of dollars of damage. In this Practical Engineering video, Grady deconstructs the accident, based on an interim report from the forensic team charged with investigating the failure. Along the way, he explains common causes of dam failures, what made the Edenville failure unusual, and how engineers build modern earthen dams to avoid this older design’s flaws. (Image and video credit: Practical Engineering)

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    Floating Bridges

    For most of history, floating bridges have been temporary structures, often used by militaries crossing water, but over the course of the twentieth century, engineers learned to build more permanent floating bridges. These structures require very particular conditions–calm waters, minimal ice, and so on–but they can be great options for crossing lakes where the traditional anchoring options for a bridge just don’t exist. In this Practical Engineering video, Grady discusses some of the challenges and innovations of these unusual bridges. (Video and image credit: Practical Engineering)

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    Protecting Wildlife from Underwater Construction

    The loud noises of construction are not just an issue for humans. Sound and pressure waves from underwater construction are a problem for water-dwellers, too. So engineers use bubble curtains around a construction site to help reduce the amount of sound that escapes. Water and air transmit sound very differently; in acoustic terms, they have very different impedance. You’ve probably experienced this yourself if you’ve ever compared the sounds of a swimming pool above and below the surface. Because some of a sound’s intensity gets lost in the water –> air –> water transition, a bubble curtain can halve the sound pressure transmitted from equipment. (Video and image credit: Practical Engineering)