science

Unified Soil Classification System

Unified Soil Classification System is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Unified Soil Classification System rather than just read about it. In short: The Unified Soil Classification System (USCS) is a soil classification system used in engineering and geology to describe the texture and grain size of a soil. The classification system can be applied to most unconsolidated materials, and is represented by a two-letter symbol.

Key takeaways

Unified Soil Classification System belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Unified Soil Classification System to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Unified Soil Classification System from memory before moving on to harder problems.

Reference excerpt

The Unified Soil Classification System (USCS) is a soil classification system used in engineering and geology to describe the texture and grain size of a soil. The classification system can be applied to most unconsolidated materials, and is represented by a two-letter symbol. Each letter is described below:

If the soil has 5–12% by weight of fines passing a #200 sieve (5% < P#200 < 12%), both grain size distribution and plasticity have a significant effect on the engineering properties of the soil, and dual notation may be used for the group symbol. For example, GW-GM corresponds to "well-graded gravel with silt." If the soil has more than 15% by weight retained on a #4 sieve (R#4 > 15%), there is a significant amount of gravel, and the suffix "with gravel" may be added to the group name, but the group symbol does not change. For example, SP-SM could refer to "poorly graded SAND with silt" or "poorly graded SAND with silt and gravel."

Symbol chart

ASTM D-2487

See also AASHTO Soil Classification System AASHTO ASTM International USDA Soil Taxonomy (Soil classification for agricultural purposes)

References Classification of Soils for Engineering Purposes: Annual Book of ASTM Standards, D 2487-83, vol. 04, American Society for Testing and Materials, 1985, pp. 395–408 Evett, Jack and Cheng Liu (2007), Soils and Foundations (7 ed.), Prentice Hall, pp. 9–29, ISBN 978-0132221382 Specific

Worked examples

Example 1 — a first encounter with Unified Soil Classification System

Start with the simplest possible case. Write down what Unified Soil Classification System claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Unified Soil Classification System before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Unified Soil Classification System ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Unified Soil Classification System

In research: Unified Soil Classification System appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Unified Soil Classification System in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Unified Soil Classification System is common in secondary-school and first-year university syllabi. It links to neighbouring topics Soil classification, so understanding it makes those chapters shorter.
In everyday life: Look for Unified Soil Classification System outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Unified Soil Classification System in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Unified Soil Classification System means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Unified Soil Classification System out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Unified Soil Classification System in simple terms?

Why does Unified Soil Classification System matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Unified Soil Classification System?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Unified Soil Classification System.