# Geotechnical Engineering Questions and Answers – Minimum Depth of Foundation: Rankine’s Analysis

«
»

This set of Geotechnical Engineering online quiz focuses on “Minimum Depth of Foundation: Rankines Analysis”.

1. The gross pressure intensity (q) of a structure is ___________
a) Total pressure at base of the footing
b) Excess pressure after the construction of the structure
c) Minimum pressure intensity at the base
d) None of the mentioned

Explanation: The gross pressure intensity q is the total pressure at the base of the footing due to the weight of the superstructure.

2. The ultimate bearing capacity and the net ultimate capacity are connected by the relation ____________
a) qf = qnf +/- σ̅ and qf = qf – σ̅
b) qf = qnf – σ̅
c) None of the mentioned
d) All of the mentioned

Explanation: The ultimate bearing capacity qf and the net ultimate capacity are connected by the following relation:
qf = qnf + σ̅ (or) qf = qf – σ̅
where σ̅ is the effective surcharge at the base level of the foundation.

3. The net safe bearing capacity is defined by which of the following equation?
a) qns=qnf / F
b) qns = qnf + σ̅
c) qns = qf – σ̅
d) All of the mentioned

Explanation: The net safe bearing capacity is the net ultimate bearing capacity divided by a factor of safety F i.e., qns = qnf/F.

4. The safe bearing capacity can also be referred as _________
a) Net safe bearing capacity
b) Ultimate bearing capacity
c) Safe bearing pressure
d) Net soil pressure

Explanation: Sometimes, the safe bearing capacity is also referred to as the ultimate bearing capacity qf divided by a factor of safety F.

5. Rankine considered the first soil element (element 1) at ___________
a) Base of the structure
b) Below the foundation
c) Edge of the footing
d) All of the mentioned

Explanation: Rankine considered the equilibrium of two soil elements, The first one immediately below the foundation (element 1).

6. The bearing capacity of cohesion-less soil at the ground surface is __________
a) Unity
b) Less than one
c) Zero
d) Greater than one

Explanation: According to Rankine’s equation bearing capacity of cohesion less soil is zero at the ground surface.

7. When a state of equilibrium is reached under the footing?
c) Safe bearing capacity of the soil is reached
d) None of the mentioned

Explanation: When the load on footing increases, and approaches a value qf, a state of plastic equilibrium is reached under the footing.

8. Rankine considered the equilibrium of second soil element at __________
a) Base of the structure
b) Below the foundation
c) Edge of the footing
d) Top of the foundation

Explanation: Rankine considered the equilibrium of the other soil element (element 2) beyond the edge of the footing, but adjacent to element 1.

9. During the state of shear failure, which of the following principal stress relationship exist?
a) σ1 = σ tan α + 2c tan α
b) σ1 = σ3 tan2 α + 2c tan α
c) σ1 = 2c tan α
d) σ1 = σ3 tan α

Explanation: During the state of shear failure (plastic equilibrium), the following principal stress relationship exists σ1 = σ3 tan2 α + 2c tan α
for cohesion-less soil,σ1 = σ3 tan2 α.

10. The symbol σ̅, represent which of the following term?
a) Ultimate bearing capacity
b) Effective surcharge
c) Gross pressure intensity
d) Bearing capacity 