Civil Engineering PE Soil Mechanics and Lab Testing 4

Question 1

A saturated clay has a total unit weight of 120 pcf and a specific gravity of solids Gs = 2.70. What is the void ratio?

Accepted Answer

0.713

Answer

0.542

Answer

1.13

Answer

0.370

Question 2

In the USCS classification, which letter symbol indicates a soil with low plasticity (LL < 50)?

Accepted Answer

L

Answer

H

Answer

W

Answer

P

Question 3

A soil sample has a mass of 185 g wet and 155 g after oven drying. What is the water content?

Accepted Answer

19.4%

Answer

16.2%

Answer

12.4%

Answer

21.0%

Question 4

Which laboratory test is used to measure the California Bearing Ratio (CBR) of a subgrade material, and what does CBR indicate?

Accepted Answer

ASTM D1883; it measures bearing capacity relative to a standard crushed rock

Answer

ASTM D2166; it measures unconfined compressive strength

Answer

ASTM D698; it measures compaction characteristics

Answer

ASTM D4767; it measures consolidated-undrained shear strength

Question 5

The effective friction angle of a sand from a drained triaxial test is 34°. If the confining pressure is 100 kPa, what is the deviator stress at failure?

Accepted Answer

274 kPa

Answer

138 kPa

Answer

200 kPa

Answer

374 kPa

Question 6

What does the coefficient of curvature (Cc) measure in a grain size distribution analysis, and what range indicates a well-graded gravel (GW)?

Accepted Answer

Cc = D30²/(D10×D60); 1 ≤ Cc ≤ 3 for GW

Answer

Cc = D60/D10; Cc ≥ 4 for GW

Answer

Cc = D10/D30; Cc < 1 for GW

Answer

Cc = D50/D10; 2 ≤ Cc ≤ 5 for GW

Question 7

A consolidation test shows that a sample reaches 90% consolidation (U=90%) at time t90 = 25 minutes. Using Taylor's square root of time fitting method, the time factor T90 = 0.848. If the drainage path is 0.5 in, what is cv?

Accepted Answer

0.00848 in²/min

Answer

0.0169 in²/min

Answer

0.00424 in²/min

Answer

0.0339 in²/min