Chapter Exam

Question 1

Strain analysis gives us the opportunity to explore the state of stress in a rock and to map out stress variations in a sample, an outcrop or a region.

Answer 1

False

Question 2

A normal stress is a force applied tangential to a plane. it does not create a volume change, but deforms a
square into o parallelogram

Answer 2

False

Question 3

General stress in a rock combination of normal and shear stresses

Answer 3

True

Question 4

In general, great deviatoric stress promotes rock fracturing

Answer 4

False

Question 5

Elasticity about how a rock responds to stress below the limit where strain becomes permanent.

Answer 5

True

Question 6

Stress measurements can also be used to estimate the amount of offset across a shear zone

Answer 6

False

Question 7

Tensile fractures or joints ore more likely to develop in rock layers with the highest Young’s modulus and the
lowest Poisson’s ratio. which in simple terms means that stiff and competent layers (e.g sandstones and limestones)
build up more differential stress than surrounding layers

Answer 7

True

Question 8

Young’s modulus characterizes how much an object that Is shortening extends perpendicular to the direction of shortening

Answer 8

False

Question 9

Boudinages are more likely to initiate in sandstones than in shale during uplift of clastic sedimentary rocks

Answer 9

False

Question 10

The closer the Poisson’s ratio gets to 0.5, the less compressible the material.

Answer 10

True

Question 11

Increasing the temperature, increasing the amount of fluid, lowering the strain rate and, in plastically deforming rocks, reducing the grain size all tend to cause strain weakening.

Answer 11

True

Question 12

Strain hardening can result in a transition from plastic to brittle deformation if the level of stress is increased.

Answer 12

True

Question 13

A decrease in temperature lowers the yield stress or weakens the rock.

Answer 13

False

Question 14

Competency is resistance of layers or objects to flow. The term is qualitative and relative to that of its neighboring layers or matrix.

Answer 14

True

Question 15

A rock with a low E-value (GPa) is mechanically weak, as its resistance to deformation is small.

Answer 15

True

Question 16

Plastic strain is recoverable because it involves stretching rather than breaking of atomic bonds

Answer 16

False

Question 17

Rheology and rock mechanics deal with the flow of rocks, while continuum mechanics primarily deals with the way rocks respond to stress by brittle faulting and fracturing.

Answer 17

True

Question 18

The effect of temperature is the main reason why flow mostly occurs in the middle and lower crust rather
than in the cool upper crust.

Answer 18

True

Question 19

Cataclastic flow involves grain rotation and frictional sliding between grains, while particulate flow also
involves grain fracturing.

Answer 19

False

Question 20

Microscopic cracks, pores and other flaws weaken rocks.

Answer 20

True

Question 21

Stress is concentrated at the tips of open microfractures in a rock, and the concentration increases with
decreasing thickness/length ratio of the microfracture.

Answer 21

True

Question 22

Cataclastic deformation bands show the most significant permeability reductions.

Answer 22

True

Question 23

Fault formation and growth is a complicated process involving a frontal process zone where microfractures
form and eventually connect.

Answer 23

True