Geotechnical Engineering Questions and Answers – The Mohr – Colomb Failure Envelope

Geotechnical Engineering Objective Questions

Civil Engineering MCQs

This set of Geotechnical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “The Mohr – Colomb Failure Envelope”.

1. The Mohr’s theory of failure can be symbolically expressed as ____________

A) τmax=F(σn) and σmax–σmin = f(σmax +σmin)
B) τmax = σmax– σmin
C) None of the mentioned
D) All of the mentioned

Answer is A)
Explanation: Mohr’s theory of failure can be symbolically expressed as: σmax–σmin = f (σmax +σmin) or τmax=f (σn).

2. The concept of a three dimension yield envelope was presented by _________

A) D.C. Drucker and Prager
B) Mohr
C) None of the mentioned
D) All of the mentioned

Answer is A)
Explanation: The effect of intermediate principal was studied by D.C. Drucker and W. Prager in 1952, who proposed the concept of a three dimensional yield envelope.

3. A major drawback of Mohr criterion is ____________

A) Shape of the envelope
B) Principal stress
C) Shape of the plane
D) All of the mentioned

Answer is A)
Explanation: The major drawback of Mohr criterion is that the curved shape of the envelope, hence the functional form of the equation τmax=F (σn) is not amendable to mathematical computation.

4. The yield or failure criterion can be expressed as ____________

A) f(I1,I2)=0
B) f(I1,I2,I3)=0
C) f(σ1,σ2,σ3)=0
D) f(σmax +σmin)

Answer is B)
Explanation: The yield criterion may be expressed as f (I1, I2, I3) = 0 Where I1, I2, I3 are the invariant of stress.

5. If the auxiliary plane in hydrostatic axis passes through the origin, then its equation is _____________

A) σ1+σ2+σ3=0
B) σ1+σ2+σ3=constant
C) I1+ I2+I3 =0
D) f(σ1,σ2,σ3)=0

Answer is A)
Explanation: If the auxiliary plane passes through the origin its equation is σ1+σ2+σ3=0 and equation will be σ1+σ2+σ3=constant if the plane is perpendicular to the hydrostatic axis.

6. The intersection of the yield surface or envelope with octahedral plane is called ____________

A) Yield point
B) Deviation point
C) Failure locus
D) Space diagonal

Answer is C)
Explanation: The intersection of yield surface with octahedral plane is called the failure locus. A point on the failure locus represents the stress state at incipient failure.

7. The hydrostatic pressure’s inability to produce failure under normal pressure was first demonstrated by ___________

A) Cross land
B) W. Pager
C) D.C. Drucker
D) Mohr

Answer is A)
Explanation: Experiments conducted by Cross land in 1965 have demonstrated that a pure state of hydrostatic pressure is unable to produce failure even under enormous pressure.

8. Which of the following equation represent hydrostatic pressure in its purest form?

A) σ1+σ2+σ3=0
B) σ1+σ2+σ3=constant
C) σ1=σ2=σ3
D) σmax+ σmin

Answer is C)
Explanation: According to cross land σ1=σ2=σ3 represent hydrostatic pressure in its purest form.

9. The Mohr-Coulomb criterion assumes that the strength of the soil is independent of ____________

A) σ1
B) σ2
C) σ3
D) All of the mentioned

Answer is B)
Explanation: The Mohr-Coulomb criterion implicitly assumes that the strength is independent of the intermediate principal stress σ2.

10. The auxiliary plane in the hydrostatic axis can also be called as ___________

A) Failure plane
B) Octahedral plane
C) Deviatoric plane
D) Principal plane

... Answer is C)
Explanation: Since all the points in the auxiliary plane represent deviatorial state of stress, the plane is also called the deviatoric plane.