Geotechnical Engineering
lesson
beginner
Introduction to Soil Mechanics: Soil Classification
A comprehensive overview of soil types, USCS classification system, and how soil properties affect engineering decisions.
Introduction to Soil Mechanics: Soil Classification — Quick Overview
Get a quick, plain-language overview of this topic.
What is Soil Mechanics?
Soil mechanics is the branch of civil engineering that deals with the behavior of soil under load and its interaction with structures.
USCS Classification System
The Unified Soil Classification System (USCS) categorizes soils into:
- Coarse-grained soils: Gravels (G) and Sands (S)
- Fine-grained soils: Silts (M) and Clays (C)
- Organic soils: Peat and organic materials
Key Index Properties
- Grain size distribution — determined by sieve analysis
- Atterberg limits — defines plasticity of fine-grained soils
- Liquid Limit (LL)
- Plastic Limit (PL)
- Plasticity Index (PI = LL - PL)
Why It Matters
Proper soil classification is essential for:
- Foundation design
- Slope stability analysis
- Embankment and earthwork projects
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