Soil Classification MCQ with answer and solution

Concept

USCS Soil Classification Symbols

Formula

No

Step-by-step solution

1. Identify USCS rules: 'W' (well-graded) applies only to coarse-grained soils (Gravel/Sand). 2. Clay (C) is a fine-grained soil classified by plasticity (L or H), making 'CW' an invalid symbol.

Explanation

In the Unified Soil Classification System (USCS), the letter W stands for well-graded, which is only used for coarse-grained soils like Gravel (GW) or Sand (SW). Fine-grained soils like Clay (C) are classified by plasticity (Low "CL" or High "CH"), making "CW" an invalid symbol.

Shortcut

To quickly identify invalid soil classification symbols in USCS: - Coarse-grained soils (Gravel 'G', Sand 'S') use **W** (Well-graded) or **P** (Poorly-graded). Examples: GW, GP, SW, SP. - **Fine-grained soils (Clay 'C', Silt 'M')** use **L** (Low plasticity) or **H** (High plasticity). Examples: CL, CH, ML, MH.**Shortcut:** "W and P are only for Sand and Gravel." Fine soils (C or M) can never have W or P attached directly to them (e.g., CW or MW are always invalid).

Common mistake

Students often mistakenly assume dual symbols like SW-SM or SC-SM are invalid because they contain hyphenated combinations, failing to recognize that dual symbols are standard USCS classifications for boundary soils.