Chapter 5 Engineering Classification of Soil

Chapter 5
5.1 Refer to Figure 5.1.

Soil Classification
A Clay
B Sandy clay
C Loam
D Sandy clay and sandy clay loam (borderline)
E Sandy loam


5.2 SOIL A: From Table 5.1, the soil is A-2-4. The GI for A-2-4 is zero.
Classification: A-2-4(0).

SOIL B: From Table 5.1, the soil is A-3. GI = 0. Classification: A-3(0).

SOIL C: From Table 5.1, the soil is A-2-6. Equation 5.2:
GI = 0.01( F200 − 15)( PI − 10) = 0.01(12 − 15)(13 − 10) = −0.09 ≈ 0
Classification: A-2-6(0)

SOIL D: From Table 5.1, the soil is A-2-7. Equation 5.2:
GI = 0.01( F200 − 15)( PI − 10) = 0.01(30 − 15)(18 − 10) = 1.2 ≈ 1
Classification: A-2-7(1)

SOIL E: From Table 5.1, the soil is A-1-b. GI = 0. Classification: A-1-b(0).


5.3 SOIL A: From Table 5.1, the soil is A-7-5. Note: PI = 21 < LL – 30 = 22
Eq. (5.1):
GI = ( F200 − 35)[0.2 + 0.005( LL − 40)] + 0.01( F200 − 15)( PI − 10)
GI = (72 − 35)[0.2 + 0.005(52 − 40)] + 0.01(72 − 15)(21 − 10)
= 15.89 ≈ 16
Classification: A-7-5(16).

SOIL B: From Table 5.1, the soil is A-6. Eq. (5.1):
GI = ( F200 − 35)[0.2 + 0.005( LL − 40)] + 0.01( F200 − 15)( PI − 10)
GI = (58 − 35)[0.2 + 0.005(38 − 40)] + 0.01(58 − 15)(12 − 10) = 5.23 ≈ 5
Classification: A-6(5)
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, SOIL C: From Table 5.1, the soil is A-7-6. Note: PI = 14 > LL – 30 = 11
Eq. (5.1):
GI = ( F200 − 35)[0.2 + 0.005( LL − 40)] + 0.01( F200 − 15)( PI − 10)
GI = (64 − 35)[0.2 + 0.005(41 − 40)] + 0.01(64 − 15)(14 − 10) = 7.9 ≈ 8
Classification: A-7-6(8)

SOIL D: From Table 5.1, the soil is A-6. Eq. (5.1):
GI = ( F200 − 35)[0.2 + 0.005( LL − 40)] + 0.01( F200 − 15)( PI − 10)
GI = (82 − 35)[0.2 + 0.005(32 − 40)] + 0.01(82 − 15)(12 − 10) = 8.86 ≈ 9
Classification: A-6(9)

SOIL E: From Table 5.1, the soil is A-6. Eq. (5.1):
GI = ( F200 − 35)[0.2 + 0.005( LL − 40)] + 0.01( F200 − 15)( PI − 10)
GI = (48 − 35)[0.2 + 0.005(30 − 40)] + 0.01(48 − 15)(11 − 10) = 2.28 ≈ 2
Classification: A-6(2)

5.4 SOIL 1: Fine fraction = % passing No. 200 sieve = 30%
Coarse fraction = 100 -30 = 70%
Gravel fraction = 100 – 70 = 30%
Sand fraction = 70 – 30 = 40%
More than 50% of coarse fraction passing No. 4 sieve, so sandy soil.
Table 5.2 and Figure 5.3: SC
Figure 5.4: More than 15% gravel. Clayey sand with gravel.

SOIL 2: Coarse fraction = 200 – 20 = 80%
Gravel fraction = 100 – 48 = 52%
Sand fraction = 80 – 52 = 28%
Table 5.2 and Figure 5.3: GC
Figure 5.4: Greater than 15% sand. Clayey gravel with sand

SOIL 3: Coarse fraction = 100 – 30 = 30%
Gravel fraction = 100 – 95 = 5%
Sand fraction = 95 – 70 = 25%
Table 5.2: fine-grained soil; LL = 52; PI = 28.
Table 5.2 and Figure 5.3: CH
Figure 5.5: ≥ 30% plus 200, % sand > % gravel, < 15% gravel,
so sandy fat clay




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