GEO TERMS: SHEAR STRENGTH OF SOIL

Question 1

a triaxial shear test is preferred to direct shear test, because _____

A. it can be performed under all three drainage conditions with complete control

B. precise measurement of pore pressure and change in volume during test, is not possible

C. stress distribution on the failure plane, is non uniform

D. none of these

Answer 1

A. it can be performed under all three drainage conditions with complete control

Question 2

the shear strength of a soil

A. is directly proportional to the angle of internal friction of the soil

B. is inversely proportional to the angle of internal friction of the soil

C. decreases with increase in normal stress

D. decreases with decrease in normal stress

Answer 2

D. decreases with decrease in normal stress

Question 3

select the incorrect statement:

A. in a direct shear box test, the plane of shear failure is
predetermined

B. better control is achieved on the drainage of the soil in a triaxial compression test

C. stress distribution on the failure plane in the case of triaxial compression test is uniform

D. unconfined compression test can be carried out on all types of soils

Answer 3

D. unconfined compression test can be carried out on all types of soils

Question 4

the angle of internal friction is least for _____

A. angular-grained loose sand
B. angular -grained dense sand
C. round-grained loose sand
D. clays

Answer 4

D. clays

Question 5

for testing a saturated clay for shear strength, the test recommended is _____

A. direct shear test
B. triaxial compression test
C. unconfined compression test
D. all the above

Answer 5

C. unconfined compression test

Question 6

the triaxial apparatus is usually used for _____

A. unconsolidated-undrained test
B. consolidated-undrained test
C. drained test
D. all the above tests

Answer 6

D. all the above tests

Question 7

shear strength of a soil is a unique function of _____

A. effective stress only
B. total stress only
C. both effective stress and total stress
D. none of the above

Answer 7

A. effective stress only

Question 8

the angle that Coulomb’s failure envelope makes with the horizontal is called _____

A. cohesion
B. angle of internal friction
C. angle of repose
D. none of the above

Answer 8

B. angle of internal friction

Question 9

the angle between the directions of the failure and the major principal plane is equal to _____

A. 90° + effective angle of shearing resistance
B. 90° + half of the shearing resistance
C. 45° - half of the shearing resistance
D. 45° + half of the shearing resistance

Answer 9

D. 45° + half of the shearing resistance

Question 10

the angle of internal friction of clay is usually _____

A. 0° to 5°
B. 5° to 20°
C. 20° to 30°
D. 30° to 45°

Answer 10

B. 5° to 20°

Question 11

failure of a slope occurs only when total shear force is _____

A. equal to total shearing strength
B. greater than total shearing strength
C. less than total shearing strength
D. none of these

Answer 11

B. greater than total shearing strength

Question 12

the angle of internal friction is maximum for _____

A. angular-grained loose sand
B. angular-grained dense sand
C. round-grained dense sand
D. round-grained loose sand

Answer 12

B. angular-grained dense sand

Question 13

a direct shear test possesses the following disadvantage:

A. a relatively thin thickness of sample permits quick drainage

B. a relatively thin thickness of sample permits quick dissipation of pore pressure developed during the test

C. as the test progresses the area under shear, gradually changes

D. none of these

Answer 13

C. as the test progresses the area under shear, gradually changes

Question 14

which one of the following statements is true for Mohr-Coulomb envelope?

A. Coulomb suggests that the relationship between shear
strength and normal stress, is adequately represented by the straight line

B. the generalized Mohr theory suggests that, though the shear stress depends on the normal stress, the relation is not linear

C. Coulomb and Mohr suggest that a definite relationship exists among the principal stress and the angle of internal friction

D. all the above

Answer 14

D. all the above

Question 15

if drainage is permitted throughout the test, during the application of both normal, and shear stresses so that full consolidation occurs and no excess pore pressure is set up at any stage of the test is known as _____

A. quick test
B. drained test
C. consolidated undrained test
D. none of these

Answer 15

B. drained test

Question 16

the shear resistance of a soil is constituted basically of the following component:

A. the frictional resistance to translocation between the
individual soil particles at their contact point

B. to the structural relation to displacement of the soil because of the interlocking of the particles

C. cohesion and adhesion between the surfaces of the soil particles

D. all the above

Answer 16

D. all the above

Question 17

select the incorrect statement:

A. effective cohesion of a soil can never have a negative value

B. effective angle of internal friction for coarse grained soils is rarely below 30°

C. effective angle of internal friction for a soil increases as
state of compactness increases

D. effective angle of internal friction is a complicated function of mineralogy and clay size content

Answer 17

A. effective cohesion of a soil can never have a negative value

Question 18

the Mohr’s straight theory is based on the following fact:

A. material fails essentially by shear

B. ultimate strength of the material is determined by the stress in the plane of slip

C. failure criterion is independent of the intermediate principal stress

D. all the above

Answer 18

D. all the above

Question 19

through a point in a loaded soil mass, there exists typical planes mutually orthogonal on which the stress is wholly normal and no shear stress acts if is

A. 1
B. 2
C. 3
D. 4

Answer 19

C. 3

Question 20

pick up the correct statement from the following:

A. failure plane carries maximum shear stress
B. failure plane does not carry maximum shear stress
C. failure plane carries shear stress equal to maximum shear stress
D. none of these

Answer 20

B. failure plane does not carry maximum shear stress

Question 21

on wetting, cohesive soils _____

A. loose permeability
B. gain shear strength
C. loose elasticity
D. decrease their shear strength

Answer 21

D. decrease their shear strength

Question 22

pick up the correct statement from the following:

A. an unconfined compression test is a special case of triaxial compression test

B. an unconfined compression test is a special case of direct shear test

C. the confining pressure is maximum during an unconfined compression test

D. the cylindrical specimen of a soil is subjected to major principal stress till it fails due to shearing along the plane of the failure

Answer 22

A. an unconfined compression test is a special case of triaxial compression test

Question 23

the direct shear test suffers from the following disadvantage:

A. drain condition cannot be controlled
B. pore water pressure cannot be measured
C. shear stress on the failure plane is not uniform
D. the area under the shear and vertical loads does not remain constant throughout the test

Answer 23

all are disadvantages of direct shear test

Question 24

the length/diameter ratio of cylindrical specimens used in triaxial test is generally _____

A. 1
B. 1.5
C. 2
D. 2.5

Answer 24

C. 2

Question 25

pick up the correct statement from the following:

A. isotropic consolidation of clay can be obtained in the triaxial apparatus under equal all-round pressure

B. if the present effective stress is the maximum to which the clay has ever been subjected, it is called normally consolidated clay

C. if the present effective stress in the past was more than present effective stress, it is called over-consolidated clay

D. all the above

Answer 25

D. all the above

Question 26

if the shearing stress is zero on two planes, then the angle between the two planes is _____

A. 45°
B. 90°
C. 135°
D. 225°

Answer 26

B. 90°

Question 27

the internal molecular attraction of a soil, the cohesion _____

A. decreases as the moisture content increases
B. increases as the moisture content decreases
C. is more in well compacted clays
D. depends upon the external applied load

Answer 27

C. is more in well compacted clays

Question 28

the shearing strength of a cohesionless soil depends upon _____

A. dry density
B. rate of loading
C. confining pressure
D. nature of loading

Answer 28

C. confining pressure

Question 29

the area of cross-section “A” at failure or during any stage of Triaxial Compression Test and its initial length (L) and volume (V) are related by the equation _____

A. A = (V + △V) / (L - △L)
B. A = (V - △V) / (L + △L)
C. A = (V - △V) / (L - △L)
D. A = (V + △V) / (L + △L)

Answer 29

C. A = (V - △V) / (L - △L)

Question 30

if a cohesive soil specimen is subjected to a vertical compressive load, the inclination of the cracks to the horizontal is _____

A. 90°
B. 45°
C. 22.5°
D. 0°

Answer 30

B. 45°

Question 31

the shear strength in undrained clay is due to _____

A. inter-granular friction
B. internal friction
C. cohesion
D. none of these

Answer 31

C. cohesion

Question 32

the vane shear test is used for the in-situ determination of the undrained strength of the intact fully saturated

A. sands
B. clays
C. gravels
D. highly organic soils

Answer 32

B. clays

Question 33

depending upon the properties of a material, the failure envelope may _____

A. be either straight or curved
B. pass through the origin of stress
C. intersect the shear stress axis
D. all the above

Answer 33

D. all the above

Question 34

the equation 𝜏 = C + σ tanφ is given by _____

A. Rankine
B. Coulomb
C. Coleman
D. Mohr

Answer 34

B. Coulomb

Question 35

through a point in a loaded soil, the principal stress is maximum on _____

A. minor principal plane
B. intermediate principal plane
C. major principal plane
D. none of these

Answer 35

C. major principal plane

Question 36

in a deposit of normally consolidated clay

A. effective stress increases with depth but water content of soil and undrained strength decrease with depth

B. effective stress and water content increase with depth but undrained strength decreases with depth

C. effective stress and undrained strength increase with depth but water content decreases with depth

D. effective stress, water content and undrained strength decrease with depth

Answer 36

C. effective stress and undrained strength increase with depth but water content decreases with depth

Question 37

cohesionless soil is _____

A. sand
B. Silt
C. clay
D. clay and silt

Answer 37

A. sand

Question 38

the shear strength of a soil

A. increases with an increase in the normal stress
B. is proportional to the cohesion of the soil
C. is generally known as the strength of the soil
D. all the above

Answer 38

D. all the above

Question 39

unconfined compressive strength test is _____

A. undrained test
B. drained test
C. consolidated undrained test
D. consolidated drained test

Answer 39

A. undrained test

Question 40

for shear strength, triaxial shear test is suitable because _____

A. it can be performed under all three drainage conditions
B. precise measurement of the pore pressure and volume change during the test is possible
C. stress distribution on the failure plane is uniform
D. all the above

Answer 40

D. all the above

Question 41

in a consolidated drained test on a normally consolidated clay, the volume of the soil sample during shear _____

A. decreases
B. increases
C. remains unchanged
D. first increases and then decreases

Answer 41

A. decreases

Question 42

at liquid limit, all soils possess _____

A. same shear strength of small magnitude
B. same shear strength of large magnitude
C. different shear small magnitude
D. different shear large magnitude

Answer 42

A. same shear strength of small magnitude

Question 43

in the triaxial compression test, the application of additional axial stress (i.e. deviator stress) on the soil specimen produces shear stress on _____

A. horizontal plane only
B. vertical plane only
C. both horizontal planes
D. all planes except horizontal and vertical planes

Answer 43

D. all planes except horizontal and vertical planes

Question 44

pick up the correct statement from the following:

A. the property of a soil that enables it to become stiff in a
relatively short time on standing is called thixotropy

B. the ratio of shear strength in natural state to the remoulded shear strength under undrained conditions is called degree of sensitivity

C. the difference between the undisturbed shear strength and remoulded shear strength is known remoulding loss

D. all the above

Answer 44

D. all the above

Question 45

select the incorrect statement:

effective angle of shearing resistance

A. increases as the size of particles increases
B. increases as the soil gradation improves
C. is limited to a maximum value of 45°
D. is rarely more than 30° for fine grained soil

Answer 45

C. is limited to a maximum value of 45°

Question 46

in a triaxial compression test when drainage is allowed during the first stage (i.e. application of cell pressure) only and not during the second stage (i.e. application of deviator stress at constant cell pressure), the test is known as _____

A. consolidated drained test
B. consolidated undrained test
C. unconsolidated drained test
D. unconsolidated undrained test

Answer 46

B. consolidated undrained test

Question 47

when drainage is permitted under initially applied normal stress only and full primarily consolidation is allowed to take place, the test is known as _____

A. quick test
B. drained test
C. consolidated undrained test
D. none of these

Answer 47

C. consolidated undrained test

Question 48

the maximum shear stress occurs on the filament which makes an angle with the horizontal plane equal to _____

A. 30°
B. 45°
C. 60°
D. 90°

Answer 48

B. 45°