# Home Work 2 DEPARTMENT OF CIVIL ENGINEERING CEGR 325 GEOTECHNICAL ENGINEERING AND LABORATORY

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DEPARTMENT OF CIVIL ENGINEERING CEGR 325 GEOTECHNICAL ENGINEERING AND LABORATORY

Home Work 2

1. A soil has 70 percent passing the No. 4 sieve and 10 percent passing the No. 200 sieve. The coefficient of uniformity is 4 and the fines are non-plastic. Classify the soil according to the Unified Soil Classification System

2. A soil sample has a liquid limit of 45 and aplastic limit of 30. Classify the soil according to the Unified Soil Classification System.

3. The following are the results of a sieve analysis:

U.S. sieve no

Mass of soil retained (g)

4

0

10

18.5

20

53.2

40

90.5

60

81.8

100

92.2

200

58.5

Pan

26.5

a. Determine the percent finer than each sieve and plot a grain-size distribution curve

b. Determine D10, D30, and D60 from the grain-size distribution curve

c. Calculate the uniformity coefficient Cu

d. Calculate the coefficient of graduation Cc

e. Classify the soil using both the ASSHTO and Unified Soil Classification Systems.

4. Following are the results from the liquid and plastic limit tests for a soil. Liquid limit tests

Number of blows, N

Moisture content (%)

16

36.5

20

34.1

28

27.0

Plastic limit test: PL =12.2 %

a. Draw the flow curve and obtain the liquid limit.

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b. What is the plasticity index of the soil ?

c. Determine the liquidity index of the soil if win situ=31%

5. A minus No. 40 material had a liquidity index of 0.73, a natural water content of 44.5 %, and a plasticity index of 24.7. Classify this soil according to the USCS, providing the group symbol for it. You do not need to graph this data; use linear interpolation if you need specific values not given.

6. Refer to the following test data:

% Passing # 200 sieve 60

Liquid Limit 55

Plastic Limit 30

What is the USCS Classification of this soil ?

7. Classify the following soils by the AASHTO classification system and give the group indices.

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8. A soil sample has 80 percent passing the No. 4 sieve and 10 percent passing the No. 200 sieve. The coefficient of uniformity is 4, while the coefficient of curvature is 2 and the fines are non-plastic. Classify the soil according to the Unified Soil Classification

9. A soil sample has a liquid limit of 50 and a plastic limit of 30. Classify the soil according to the Unified Soil Classification

10. Explain briefly why it is preferable, in plotting GSD (Grain Size Distribution) curves, to plot the grain diameter on a logarithmic rather than an arithmetic scale

Are the shapes of GSD curves comparable (for example, do they have the same Cu and Cc) when plotted arithmetically? Explain.