Lesson 2/Learning Event 2
Learning Event 2
CLASSIFY COARSE- AND FINE-GRAINED SOILS
Coarse-grained Soils with Less than 5 Percent Fines
If a coarse-grained soil has less than 5 percent fines, the fines will not significantly affect the
construction properties of the soil. Soils with less than 5 percent fines are, therefore, classified
according to the gradation of the coarse fraction (Figure 13).
FIGURE 13. SOIL CLASSIFICATION CHART
The possible classifications for a coarse-grained soil with less than 5 percent fines are:
GW (Well-Graded Gravel)
GP (Poorly-Graded Gravel)
SW (Well-Graded Sand)
SP (Poorly-Graded Sand)
Remember that any point falling in the box on the bottom of the A-line on the Casagrande Plasticity
Chart cannot be classified solely as either silt or clay. It is classified as a combination of both. The first
and third letter of
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