Geotechnical Engineering — Quiz 4

Questions in this quiz (10)

1. A uniform soil has a unit weight of $$110\ \mathrm{lb/ft^3}$$. The water table is $$6.5$$ ft below the surface. At a depth of $$11$$ ft, the effective vertical stress in the soil is most nearly:

   • 800 lb/ft^2
   • 900 lb/ft^2
   • 1200 lb/ft^2
   • 1900 lb/ft^2

2. A shrinkage limit test yields the following data: initial wet mass $$=48.6\ \mathrm{g}$$, dry mass $$=31.2\ \mathrm{g}$$, initial volume $$=30.5\ \mathrm{cm^3}$$, and dry volume $$=20.4\ \mathrm{cm^3}$$. Assuming the density of water is $$1.0\ \mathrm{g/cm^3}$$, calculate the shrinkage limit.

   • 29.8%
   • 34.6%
   • 23.4%
   • 31.2%

3. A soil has a cohesion $$c=22\ \mathrm{kPa}$$ and an angle of internal friction $$\phi=28^\circ$$. Using the Mohr-Coulomb failure criterion, calculate the shear strength of the soil on a plane where the normal stress is $$140\ \mathrm{kPa}$$.

   • 96.5 kPa
   • 88.4 kPa
   • 103.2 kPa
   • 75.8 kPa

4. An unconfined compression test on a saturated clay sample yields an unconfined compressive strength of $$160\ \mathrm{kPa}$$. Assuming $$\phi=0$$ conditions, what is the undrained shear strength of the clay?

   • 80 kPa
   • 160 kPa
   • 40 kPa
   • 120 kPa

5. A field density test indicates that the in-place dry unit weight of a compacted fill is $$16.2\ \mathrm{kN/m^3}$$. The maximum dry unit weight from the Standard Proctor test is $$18.0\ \mathrm{kN/m^3}$$. Calculate the relative compaction.

   • 90.0%
   • 85.5%
   • 92.8%
   • 88.2%

6. Two direct shear tests are performed on a soil sample with the following results: Test 1: normal stress $$=60\ \mathrm{kPa}$$, shear stress at failure $$=42\ \mathrm{kPa}$$ Test 2: normal stress $$=180\ \mathrm{kPa}$$, shear stress at failure $$=108\ \mathrm{kPa}$$ Determine the angle of internal friction.

   • 30.4°
   • 33.7°
   • 28.6°
   • 35.2°

7. An unconsolidated-undrained triaxial test is conducted on a saturated clay sample. The cell pressure is $$120\ \mathrm{kPa}$$ and the major principal stress at failure is $$300\ \mathrm{kPa}$$. Determine the undrained shear strength of the clay.

   • 90 kPa
   • 75 kPa
   • 60 kPa
   • 105 kPa

8. A granular soil has an effective friction angle $$\phi = 36^\circ$$. Using Rankine's theory, determine the coefficient of passive earth pressure.

   • 3.25
   • 2.78
   • 0.31
   • 1.95

9. A retaining wall supports a cohesionless backfill with unit weight $$\gamma = 17.8\ \mathrm{kN/m^3}$$ and friction angle $$\phi = 30^\circ$$. Using Rankine's theory, calculate the active earth pressure at a depth of $$4\ \mathrm{m}$$ below the ground surface.

   • 24.0 kPa
   • 36.5 kPa
   • 48.2 kPa
   • 18.6 kPa

10. A retaining wall $$5\ \mathrm{m}$$ high supports a cohesionless backfill with unit weight $$\gamma = 18.2\ \mathrm{kN/m^3}$$ and friction angle $$\phi = 34^\circ$$. Using Rankine's theory, calculate the total active force per unit length of wall.

    • 142.5 kN/m
    • 168.4 kN/m
    • 125.6 kN/m
    • 189.3 kN/m