Sandcastle Holds Up a Car Through Clever Engineering!

Interesting Engineering

Almost every child loves a good sandcastle. However, building a tall one can prove to be a tedious task since sand has a tendency to shear off and collapse, resembling something similar to a sad pyramid rather than a magnificent castle. However, with some clever engineering, shearing can be prevented with some simple modifications.

Sand is held together by frictional forces, the more friction, the more supportive the sand can become. Of course, any sand engineer (often found at the beach with a colorful plastic shovel and bucket) can tell you that water can be added to increase the resistance against shearing, or preventing the sand from sliding off. Generally, granular material (like sand) cannot stand vertically since the sand does not have enough contact points to hold it together, causing pieces to slide off and causing the structure to fail. The angle of repose, or the maximum angle that soil can naturally rest. Any steeper and the soil will slide off, creating a volcano-styled structure.

shear strength[Image Source: Practical Engineering]

This shearing can be prevented by adding layers that provide tensional forces that act perpendicular to the shearing planes, resisting the movement and preventing the structure from failing. A few sheets of a thin material is all it takes to support the partial weight of a car with almost no movement. Of course, civil engineers make use of this practical phenomena by adding layers of materials where granular materials require reinforcement, such as in seawalls and retaining walls on motorways. This simple trick provides a cheap alternative building structure that is surprisingly strong.  You probably drive by structures that use this technique every single day.

sandcastle holding car[Image Source: Practical Engineering]

Now, you can use this trick to prove that you can stand atop a mound of sand by simply applying a few thin sheets of material. This ingenious technique is both incredibly useful, very fun, and of course very important to all types of geotechnical and civil engineers. Naturally, as being immensely intrigued by crushing things under intense force, we would love to see the Hydraulic Press Channel try and fail this sandcastle – has the hydraulic press finally met its match? I think we all would like to find out.

SEE ALSO: What does a Civil Engineer Do?

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