Soil Classification – Why Do we Have it?
2.1.1 Introduction to Soil Classification
Do you remember back when you were in college? What did your professor in that required soil mechanics class say about soil classification? He probably said that geotechnical engineers the world over need to communicate with one another about the types of soils they are studying. They need a common soil-language to help other engineers understand what type of soil they have on their site or in their laboratory. As a result, nearly every published geotechnical paper has an introductory section describing the soil’s geology, color, grain-size distribution, dry unit weight, Atterberg limits, Unified Soil Classification or AASHTO Soil Classification, water content, percentage organic content, relative density, friction angle, undrained shear strength, and so on.
Below I’ll explain what standard classification tests are communicating to experienced geotechnical engineers.
2.1.2 Soil Properties Suggested by Classification Tests
Before we dive into a discussion of soil classification tests, there are a couple of basic questions to consider. When we think about soil what do we imagine it to be? What does the ideal soil look like and what does the ideal water look like? These seem to be simple or trivial questions, but please bear with me for a couple of pages because the answers to these questions significantly impact how you think about soil mechanics.
When most of us visualize a soil, we picture a ...