Question 3.22: The following data refers to a silty clay that was assumed t...

Liquidity Index, I_{l}=\frac{w_{n}-w_{p}}{w_{l}-w_{p}}=\frac{22-20}{45-20}=0.08

Sensitivity, S=\frac{q_{u} \text { undisturbed }}{q_{u}^{\prime} \text { disturbed }}=\frac{244}{144}=1.7

Void ratio, e=\frac{V}{V_{s}}

For S=1, e=w G_{s}=0.22 \times 2.7=0.594.

Unified Soil Classification

Use the plasticity chart Fig. 3.22 w_{l}=45, I_{p}=25. The point falls above the A-line in the CL-zone, that is the soil is inorganic clay of low to medium plasticity.

AASHTO System

Group Index G I=0.2 a+0.005 a c+0.01 b d

a = 90 – 35 = 55

b = 90 – 15 = 75

c = 45 – 40 = 5

d = 25 – 10 = 15 \text { (here } \left.I_{p}=w_{l}-w_{p}=45-20=25\right)

Group index G I=0.2 \times 55+0.005 \times 55 \times 5+0.01 \times 75 \times 15

Enter Table 3.15 with the following data

% passing 200 sieve = 90%

Liquid limit = 45%

Plasticity index = 25%

With this, the soil is either A-7-5 or A-7-6. Since \left(w_{l}-30\right)=(45-30)=15<25\left(I_{p}\right) the soil is classified as A-7-6. According to this system the soil is clay, A-7-6 (24).