Houghton – Atterberg Liquid Limits Machine

How it works

The Liquid Limits Machine is a tool that helps scientists figure out when soil changes from being liquid (like mud), to becoming more like playdough (Soft and squishy). This happens when there’s enough water in the soil which is called the “Liquid Limit.” To find this out, the machine taps the soil in a brass cup a certain number of times until the soil starts sticking back together.

There are a few different types of this machine:

1. Fully Manual – These machines have a hand crank that you turn
2. Manual with a counter – These machines have a hand crank and a timer, so you don’t have to keep track as you perform the test
3. Fully Automatic – These machines have a motor and counter so you don’t have to be hands on.

Each machine has a brass cup that drops the soil exactly 1 centimeter onto a rubber base, which is really important for getting accurate results. You can also easily take the cup off the machine to clean it after you’re done. This tool helps engineers test soil for construction projects, making sure the ground is just right before they start building.

Why it’s used

When people want to build roads, bridges, or buildings, they need to make sure the soil underneath is strong enough to hold everything up. To figure this out, scientists and engineers use a test called the Atterberg Limits Test. This test can help them understand how soil behaves when it has different amounts of water in it. This is just as important in water heavy areas as well as in dry desert.

In the early 1900s, a chemist from Sweden, named Albert Atterberg, came up with this test, and another scientist named Arthur Casagrande made the tests even better for construction. These tests are super important because soil can change a lot when it gets wet (Think shrink swell soil and the lopsided foundations that resulted). For example, if soil is too wet, it can turn into mud that’s too weak to hold up a building.

There are three important Atterberg Limits tests:

1. Liquid Limit Test: This test checks how much water can be added to the soil before it turns from soft and squishy to more like a thick liquid. To do this, the soil is placed in a special cup, and the cup is tapped on a hard surface over and over again. The more water in the soil, the more it flows like a liquid. When the groove in the soil closes after 25 taps, that’s when they know they’ve reached the liquid limit.
2. Plastic Limit Test: This test checks when the soil changes from being soft and moldable, like playdough, to crumbly and breakable. The soil is rolled into thin little strings, and when it starts breaking apart easily, that’s called the plastic limit. If the soil holds together well, it’s still in its plastic state. When it starts breaking, it means there’s not enough water left for the soil to stay together.
3. Shrinkage Limit Test: This test checks how much soil shrinks when it dries out. As the soil dries, it gets smaller, but at a certain point, it won’t shrink anymore, no matter how dry it gets. That point is called the shrinkage limit. Engineers need to know this because soil that shrinks too much could cause problems if a building or road is on top of it.

When soil changes from dry to wet, it goes through different stages. At first, it’s a solid, hard material. As it gets wetter, it becomes more crumbly (semi-solid), then moldable like clay (plastic), and finally, it turns into a liquid-like state. Each of these stages happens at a different level of water in the soil, which is why these tests are important.

Knowing the results of these tests helps engineers decide what kind of soil they can build on. For example, if the soil has too much clay and turns into a liquid when wet, it might not be good for building. But if the soil stays strong even when it gets wet, it might be perfect for construction. This also helps them predict how the soil will behave if it rains a lot or if it dries out during a drought.

By testing the soil’s limits with these tests, engineers can make sure they are building on soil that will be safe and strong enough to support everything.