ELI5: Explain Like I'm 5

Direct shear test

Okay kiddo, let's learn about direct shear tests!

So imagine you have a piece of sand or soil that you want to test to see how strong it is. A direct shear test is a way to do that.

First, you take a sample of the sand or soil and put it in a special box called a shear box. The box has two parts - a top part and a bottom part - and they can slide past each other.

Next, you put a weight on top of the sample to apply pressure to it. This is called the normal stress. It's like if you put a heavy book on a pile of sand - the sand gets squished down by the weight of the book.

Then you slide the top part of the box sideways, while keeping the bottom part steady. This is called the shear stress. It's like if you put your hands on opposite sides of a pile of sand and push them in opposite directions - the sand in the middle will start to crack and move apart.

As you slide the top part of the box, you measure how much force it takes to move it. This tells you how strong the sand or soil is.

Scientists and engineers use direct shear tests to figure out how much weight a building or a bridge can hold before the ground underneath starts to give way. It's important to know this so they can make buildings and bridges that are safe for people to use.

And that's how a direct shear test works, kiddo!