TABLE OF CONTENTS The following notation is used in this chapter:
| Symbol | Definition |
|---|---|
| C c | Compression index (soil compressibility, Table 5.4) |
| C c | Coefficient of curvature [for soil classification, Eq. (4.9)] |
| C u | Coefficient of uniformity [for soil classification, Eq. (4.8)] |
| e 0 | Void ratio of soil |
| F | Percent fines (i.e., percent passing no. 200 sieve) |
| G | Specific gravity (soil solids plus organic matter, Table 5.4) |
| LL | Liquid limit |
| PI | Plasticity index |
| PL | Plastic limit |
| s u | Undrained shear strength |
| S t | Sensitivity of cohesive soil |
| w | Water content of soil |
| t | Total unit weight |
The purpose of soil classification is to provide the geotechnical engineer with a way to predict the behavior of the soil for engineering projects. There are several different soil classifications in use. The more commonly used soil classification systems are described in this chapter. An important part of soil classification is the particle size distribution and the Atterberg limits (see Chap. 4).
In the United States, the most widely used soil classification system is the Unified Soil Classification System (U.S. Army 1960, Howard 1977). The Unified Soil Classification System is abbreviated USCS (not to be confused with the U.S. Customary System, which could have the same abbreviation). The USCS was initially developed by Casagrande (1948) and then later modified by Casagrande in 1952.
The USCS separates soils into two main groups: coarse-grained soils and finegrained soils. The basis of the USCS is that the engineering...
