1.

M (Silt).

The material is fine-grained. The Liquid Limit and the

1

Plasticity Index plot below the A-line on the Plasticity

Chart.

2.

G (Gravel)

1

3.

S or G/W or P

1

4.

SP

The soil is coarse grained (the percentage of fines is less than

2

or equal to 50 percent). The predominant coarse-grained

fraction is sand, so the primary letter is S. There are less than 5

percent fines, so gradation will determine the secondary letter.

Because Cu is not greater than 6 (for sand), the soil is poorly

graded, therefore the secondary letter is P.

5.

USCS Symbol: GM-GC

2

The soil is coarse-grained. The predominant coarse-grained

fraction is gravel (51 percent). The primary letter therefore is G.

Subtracting the PL from the LL we find that the PI is 6 percent.

Plotting the LL and PI on the plasticity chart we see that the

point falls within the box at the base line of the A-line, indicating

that a dual classification will be used. The first and third letters

are G, the second letter is M, and the fourth letter is C.

6.

USCS Symbol: SM.

2

The amount of fines is 40 percent which is less than 50 percent.

Therefore, the soil is coarse-grained. The primary letter is S since

sand is the predominant coarse fraction. As there are more than 12

percent fines, the type of fines will govern the selection of a

secondary letter. The LL of 63 percent and the PI of 15 percent plot

below the A-line on the plasticity chart indicating that the fines are silty.

The secondary letter, therefore, is M (the symbol for silt).