Civil Engineering PE Soil Mechanics and Lab Testing 2

Question 1

A standard Proctor compaction test yields a maximum dry unit weight of 112 pcf at an optimum moisture content of 14%.
If the field dry unit weight is 107 pcf at 13% moisture, what is the relative compaction?

Accepted Answer

95.5%

Answer

91.1%

Answer

85.7%

Answer

98.2%

Question 2

In a triaxial consolidated-undrained (CU) test, pore water pressure is measured. If the total minor principal stress is 100 kPa and the pore pressure at failure is 40 kPa, what is the effective minor principal stress?

Accepted Answer

60 kPa

Answer

140 kPa

Answer

100 kPa

Answer

40 kPa

Question 3

A consolidation test on a 0.75-inch thick sample (double drainage) reaches 50% consolidation in 8 minutes. What is the coefficient of consolidation (cv) in in²/min?

Accepted Answer

0.00527 in²/min

Answer

0.0211 in²/min

Answer

0.00132 in²/min

Answer

0.0844 in²/min

Question 4

Which ASTM standard governs the Atterberg Limits test (liquid limit and plastic limit) for soils?

Accepted Answer

ASTM D4318

Answer

ASTM D1557

Answer

ASTM D2216

Answer

ASTM D6913

Question 5

A soil has a liquid limit of 52 and a plastic limit of 26. What is the plasticity index, and how is it classified on the plasticity chart?

Accepted Answer

PI = 26, plots in CH zone

Answer

PI = 26, plots in CL zone

Answer

PI = 78, plots in MH zone

Answer

PI = 52, plots in CH zone

Question 6

In a constant-head permeability test, a sample 10 cm long and 50 cm² in cross-section passes 320 cm³ in 4 minutes under a head of 25 cm. What is the hydraulic conductivity?

Accepted Answer

0.0107 cm/s

Answer

0.0427 cm/s

Answer

0.00267 cm/s

Answer

0.107 cm/s

Question 7

A sand layer has D10 = 0.15 mm and D60 = 0.75 mm. What is the coefficient of uniformity (Cu)?

Accepted Answer

5.0

Answer

0.20

Answer

1.25

Answer

4.5