MCQ Soil mechanics questions (Soil shear strength).pdf

MCQ soil mechanics

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Soil shear strength
1. What does the direct shear test directly measure for a soil sample?
A) Hydraulic conductivity
B) Compressibility
C) Shear strength
D) Permeability
E) Plasticity index

2. In a direct shear test, which of the following parameters are primarily determined?
A) Cohesion and unit weight
B) Cohesion and angle of internal friction
C) Bulk density and porosity
D) Consolidation and permeability
E) Void ratio and water content

3. Which of the following is NOT an outcome of the direct shear test?
A) The maximum shear stress the soil can bear
B) The soil's angle of internal friction
C) The effective cohesion of the soil
D) The soil's permeability coefficient
E) The failure envelope for the soil

4. What role does the normal stress play in a direct shear test?
A) It is applied to increase the soil's permeability
B) It controls the moisture content of the soil sample
C) It is used to consolidate the soil before testing
D) It affects the shear strength by altering the soil's internal friction
E) It is irrelevant to the test outcomes

5. How is the angle of internal friction (φ) determined from the results of a direct shear
test?
A) By measuring the change in volume of the soil sample
B) Through the application of varying weights and measuring displacement
C) By calculating the slope of the failure envelope on a plot of shear stress versus
normal stress
D) By observing the change in moisture content of the soil
E) It is assumed based on the soil type prior to testing

6. What is primarily measured in a direct shear test to determine soil shear
strength?
A) The maximum pressure applied on the soil
B) The change in soil volume under pressure
C) The shear stress at which soil initially fails

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D) The moisture content of the soil at failure
E) The time taken for soil to consolidate under pressure

7. Which parameters are directly obtained from a direct shear test?
A) Cohesion and angle of internal friction
B) Bulk density and porosity
C) Permeability and seepage velocity
D) Compressibility and consolidation
E) Elastic modulus and Poisson's ratio

8. How is the failure plane determined in a direct shear test?
A) It is predetermined by the testing apparatus
B) It forms naturally based on the soil's weakest plane
C) It is calculated using the Mohr-Coulomb failure criterion
D) It is identified through X-ray diffraction after the test
E) It is assumed to be horizontal and is manually adjusted

9. In a direct shear test, what does the slope of the shear stress-displacement curve
indicate about the soil's shear strength?
A) It indicates an increase in soil's shear strength with depth.
B) It signifies the elastic limit of the soil under shear stress.
C) It reflects the constant volume of soil during shearing.
D) It shows the residual strength of the soil.
E) It represents the dilatancy of the soil under shear stress.

10. What is the significance of performing a direct shear test under different normal
stresses?
A) To determine the effect of water content on shear strength
B) To understand the change in soil's permeability with stress
C) To find the soil's cohesion and angle of internal friction accurately
D) To measure the consolidation settlement of soil under load
E) To assess the soil's compaction characteristics

11. What is the primary reason for applying incremental normal stresses in a direct
shear test?
A) To simulate the natural soil layering
B) To determine the soil's optimum moisture content
C) To assess the soil's compressibility under load
D) To establish a relationship between normal stress and shear strength
E) To measure the soil's hydraulic conductivity under different pressures

12. During a direct shear test, if a soil sample fails at a lower shear stress under a
higher normal stress, what could be the implication?
A) The soil is purely cohesive

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B) The soil has a high angle of internal friction
C) The sample was not properly prepared
D) The soil has low cohesion and low angle of internal friction
E) The testing apparatus was not calibrated properly

13. Why is it important to ensure that the shear plane in a direct shear test is
predefined?
A) To accurately measure the soil's permeability
B) To prevent any vertical displacement during shearing
C) To ensure that failure occurs along a specific plane for reliable shear strength
measurement
D) To control the moisture content of the sample during testing
E) To simulate the effect of seismic activities on soil layers

14. Which factor does NOT affect the accuracy of shear strength parameters
obtained from the direct shear test?
A) The rate of shear strain application
B) The initial moisture content of the soil sample
C) The thickness of the soil sample
D) The temperature in the testing room
E) The size of the soil particles

15. What is the significance of plotting the failure envelope in a direct shear test?
A) It helps in determining the soil's permeability characteristics
B) It allows for the calculation of the soil's maximum dry density
C) It is used to determine the soil's cohesion and angle of internal friction
D) It indicates the optimal moisture content for soil compaction
E) It provides a measure of the soil's plastic and liquid limits

16. What does the direct shear test directly measure?
A) The maximum and minimum void ratios of soil
B) The consolidation properties of soil
C) The shear strength of a soil sample
D) The permeability of soil
E) The plasticity index of soil

17. In a direct shear test, what are the primary shear strength parameters obtained?
A) Bulk density and particle density
B) Cohesion and angle of internal friction
C) Porosity and permeability
D) Liquid limit and plastic limit
E) Dry density and wet density

18. Which factor is not considered a limitation of the direct shear test?

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A) The test does not allow for the measurement of pore water pressure.
B) The shear plane is predetermined, which may not represent natural conditions.
C) The test can only be conducted on granular soil types.
D) The state of stress during the test may not accurately represent field conditions.
E) The test requires a relatively large sample size compared to other tests.

19. How is the angle of internal friction (φ) determined from the results of a direct
shear test?
A) By measuring the change in volume of the soil sample during shearing
B) Through the calculation of the soil's plasticity index
C) By plotting the shear stress against normal stress and finding the slope of the best-
fit line
D) By determining the moisture content at which soil changes from the liquid state to
the plastic state
E) By calculating the ratio of void ratio to particle density

20. Why is the direct shear test preferred for determining the shear strength
parameters of coarse-grained soils?
A) Because it can accurately measure the pore water pressure in coarse-grained soils
B) Because coarse-grained soils are too permeable for triaxial tests
C) Because it simulates the natural conditions under which most coarse-grained soil
layers fail
D) Because it is the only test that can be used on both saturated and unsaturated
samples of coarse-grained soils
E) Because it provides the most accurate measurement of cohesion in coarse-grained
soils

21. What is the significance of the normal stress applied in a direct shear test?
A) It simulates the self-weight of the soil.
B) It measures the soil's resistance to erosion.
C) It determines the soil's optimum moisture content.
D) It represents the pre-consolidation stress of the soil.
E) It simulates the overburden pressure in field conditions.
22. During a direct shear test, how is the shear stress at failure determined?
A)By dividing the peak shear load by the area of the shear plane at failure.
B) By calculating the difference between the initial and final vertical loads.
C) By measuring the decrease in volume of the soil sample.
D) By the total displacement of the soil sample at failure.
E) By the change in moisture content of the soil sample.
23. Which of the following is a true statement about the preparation of samples for a
direct shear test?
A) Samples must be fully saturated to ensure accurate results.
B) The soil sample is compacted to a predetermined density and moisture content.

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C) All samples must be air-dried before testing.
D) Organic soils are preferred for direct shear testing due to their cohesive nature.
E) The test is most accurate with remoulded samples to simulate natural soil
conditions.
24. What does a horizontal line on a direct shear test plot (shear stress vs.
displacement) indicate?
A) The soil sample has reached its ultimate shear strength.
B) The test apparatus has malfunctioned.
C) The soil is purely cohesive with no internal friction.
D) The soil has undergone strain softening.
E) Residual shear strength is being measured.
25. Why might a geotechnical engineer prefer the direct shear test over other shear
strength tests for certain projects?
A) It requires less advanced equipment and is simpler to perform.
B) It is the only test that can provide the shear modulus of soil.
C) It can accurately simulate the complex stress conditions found in nature.
D) It is faster and provides immediate results compared to triaxial compression
tests.
E) All of the above.
26. What is the effect of increasing the normal stress in a direct shear test?
A) Decreases the angle of internal friction
B) Increases the cohesion of the soil
C) Increases the shear strength of the soil
D) Has no effect on the shear strength parameters
E) Decreases the cohesion of the soil
27. Which statement best describes the failure plane in a direct shear test?
A) It is always horizontal and occurs at the weakest point within the soil sample.
B) The failure plane is predetermined by the design of the test apparatus.
C) It can be adjusted according to the soil type being tested.
D) The failure plane occurs at an angle equal to the angle of internal friction of the
soil.
E) It is dependent on the moisture content of the soil sample.
28. In the context of a direct shear test, what is the primary reason for plotting the
shear stress versus normal stress?
A)To determine the cohesive strength of the soil
B) To find the optimum moisture content for soil compaction
C) To calculate the soil's permeability coefficient
D) To establish the soil's failure envelope
E) To measure the soil's consolidation under load
29. How does the direct shear test address the shear strength of unsaturated soils?

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A) By applying a suction pressure to simulate unsaturation
B) It does not directly measure the shear strength of unsaturated soils
C) By pre-saturating the soil samples before testing
D) By adjusting the shear rate to account for capillary forces
E) By measuring the water content variation during the test
30. Which material condition is typically NOT suitable for testing with a direct shear
test?
A) Loose sand
B) Dense gravel
C) Soft clay
D) Highly organic peat
E) Saturated silt
31. What aspect of soil behaviour is primarily investigated in a consolidated
undrained triaxial shear test?
A) The effect of pore water pressure on shear strength
B) The maximum dry density achievable
C) The soil's permeability under shear
D) The elastic modulus of the soil
E) The impact of soil structure on cohesion

32. In the analysis of direct shear test results, a linear failure envelope indicates
which of the following soil conditions?
A) The soil behaves in a perfectly plastic manner
B) The soil exhibits both cohesive and frictional resistance
C) The soil is purely frictional with no cohesion
D) The cohesion of the soil is zero
E) Both B and C are correct

33. Why is the direct shear test often criticized in geotechnical engineering
practices?
A) It provides unrealistic consolidation conditions.
B) It assumes a uniform stress distribution across the failure plane.
C) It can only be used for fine-grained soils.
D) It overestimates the angle of internal friction for most soils.
E) It cannot measure pore water pressures developed during shearing.

34. When interpreting direct shear test data, a nonlinear failure envelope on a plot of
shear stress vs. normal stress typically indicates what about the soil sample?
A) The presence of large particles obstructing the shear plane
B) An incorrect application of the normal stress
C) Non-homogeneity within the soil sample
D) The soil exhibits strain-hardening behaviour
E) Varied angles of internal friction at different normal stresses

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35. How does the rate of shearing in a direct shear test affect the measured shear
strength of clayey soils?
A) Faster shearing rates typically increase measured shear strength due to rapid
pore pressure build-up.
B) Slower shearing rates result in higher shear strength because of soil
consolidation.
C) The rate of shearing has no significant effect on the shear strength of clayey
soils.
D) Faster shearing rates decrease the shear strength due to thermal effects.
E) Slower shearing rates increase the pore water pressure, reducing measured
shear strength.
36. When performing a triaxial shear test on a sandy soil sample, what is the
primary reason for applying a confining pressure?
A) To simulate the effect of water table fluctuations on the soil's shear strength.
B) To prevent soil particles from escaping the shear box during the test.
C) To simulate the in-situ lateral stress conditions the soil experiences.
D) To enhance the cohesion between soil particles for accurate measurement.
E) To control the rate of shear and ensure uniform deformation.

37. Which statement correctly describes a limitation of the direct shear test related
to the determination of failure planes?
A) The failure plane is artificially created and may not represent the plane of weakness
in situ.
B) The test can only identify a single failure plane, which is not realistic for
heterogeneous soils.
C) Failure planes determined by the test are always parallel to the horizontal axis, which
is rarely the case in natural conditions.
D) The method assumes a circular failure plane, which is not accurate for anisotropic
materials.
E) The failure plane is determined after the test, making it difficult to prepare samples
correctly.

38. In direct shear testing, why is it important to measure the displacement along the
shear plane?
A) It provides a direct measure of the soil's elasticity.
B) Displacement measurements help in calculating the exact volume change during
shearing.
C) The magnitude of displacement at peak shear strength is used to classify the soil
type.
D) The displacement helps in understanding the post-peak behaviour of the soil,
indicating whether it softens or hardens.
E) It determines the hydraulic conductivity parallel to the shear plane.

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39. What is the primary challenge in interpreting the results of direct shear tests on
highly plastic clays?
A) The tests tend to overestimate the angle of internal friction.
B) Plastic clays can adhere to the shear box, affecting the shear resistance
measurement.
C) The slow drainage of water from plastic clays can lead to inaccurate pore pressure
measurement.
D) High plasticity clays do not show a distinct peak in shear strength, making it
difficult to determine failure criteria.
E) The results are highly sensitive to the initial water content of the clay, leading to
variability in outcomes.

40. What is the primary reason for performing multiple direct shear tests at
different normal stresses on the same soil type?
A) To determine the effect of soil density on shear strength.
B) To create a failure envelope from which the cohesion and angle of internal friction
can be derived.
C) To understand how soil moisture content affects shear strength.
D) To assess the variability in soil sample properties across a site.
E) To calculate the soil's permeability coefficient under varying pressures.

41. A sample of clay soil has a cohesion (c) of 25 kPa and an angle of internal friction
(ϕ) of 0 degrees. If a normal stress (σ) of 100 kPa is applied to the soil sample,
what is the shear strength (τ) of this soil?
A) 25 kPa
B) 100 kPa
C) 125 kPa
D) 150 kPa
E) 175 kPa

42. A sandy soil sample has an angle of internal friction ϕ) of 30 degrees and
negligible cohesion (c=0). If a normal stress (σ) of 200 kPa is applied to this soil
sample, what is the shear strength (τ) of this soil?
A) 100 kPa
B) 115.47 kPa
C) 200 kPa
D) 346.41 kPa
E) 400 kPa

43. A cohesive soil has a cohesion (c) of 50 kPa and an angle of internal friction (ϕ) of
0 degrees. What is the maximum shear strength (τmax) that can be achieved if the
normal stress (σ) is doubled from 100 kPa to 200 kPa?
A) 50 kPa
B) 100 kPa
C) 150 kPa

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D) 200 kPa
E) 250 kPa

44. Consider a soil sample with a cohesion (c) of 10 kPa and an angle of internal
friction (ϕ) of 25 degrees. The soil is currently under a normal stress (σ) of 150
kPa. Calculate the increase in shear strength (Δτ) if the normal stress is increased
to 250 kPa.
A) 46.63 kPa
B) 76.34 kPa
C) 93.97 kPa
D) 110.61 kPa
E) 128.25 kPa

45. A saturated soil sample has a total vertical stress σ) of 180 kPa and a pore water
pressure (u) of 60 kPa. If the soil has a cohesion (c) of 20 kPa and an angle of
internal friction (ϕ) of 30 degrees, calculate the effective shear strength (τ) of the
soil.
A) 89.28 kPa
B) 164.85 kPa
C) 188.56 kPa
D) 210.72 kPa
E) 235.89 kPa

46. What does soil shear strength refer to?
A) The ability of soil to resist compression
B) The resistance of soil to shearing stresses
C) The capacity of soil to retain water
D) The degree of soil fertility
E) The ability of soil to conduct electricity

47. Which of the following factors influences soil shear strength?
A) Temperature
B) Soil colour
C) Moisture content
D) Air pressure
E) Soil texture

48. Which test is commonly used to measure soil shear strength?
A) Density test
B) pH test
C) Direct shear test
D) Alkalinity test
E) Atterberg limits test

49. What does cohesion represent in soil shear strength?
A) The resistance of soil to shearing due to friction
B) The interparticle forces within cohesive soils
C) The angle of internal friction

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D) The density of soil particles
E) The porosity of soil

50. Granular soils such as sand typically exhibit:
A) High cohesion and low internal friction
B) Low cohesion and high internal friction
C) High cohesion and high internal friction
D) Low cohesion and low internal friction
E) Medium cohesion and medium internal friction

51. What parameter describes the resistance of soil to shear deformation due to friction
between soil particles?
A) Cohesion
B) Angle of internal friction
C) Density
D) Porosity
E) Permeability

52. Which criterion is commonly used to describe the relationship between shear stress
and normal stress on a plane within a soil mass?
A) Hooke's Law
B) Mohr-Coulomb failure criterion
C) Archimedes' principle
D) Bernoulli's principle
E) Pascal's Law

53. Failure in soil occurs when the shear stress on a plane reaches a critical value
determined by:
A) Density and moisture content
B) Cohesion and porosity
C) Cohesion and angle of internal friction
D) pH and temperature
E) Friction and compaction

54. Which type of soil is primarily composed of organic matter and lacks significant
cohesion?
A) Clay
B) Sand
C) Silt
D) Peat
E) Loam

55. What effect does an increase in moisture content typically have on the shear strength
of cohesive soils?
A) Increases cohesion and decreases angle of internal friction
B) Decreases cohesion and increases angle of internal friction
C) Increases both cohesion and angle of internal friction
D) Decreases both cohesion and angle of internal friction
E) Has no significant effect on shear strength

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56. The failure criteria for a material under complex loading conditions often depend on
which of the following?
A) The minor principal stress only
B) The colour of the material
C) The temperature of the environment
D) The major principal stress only
E) Both the major and minor principal stresses
Answer: E) Both the major and minor principal stresses

57. What is the definition of major principal stress in a material under load?
A) The smallest stress experienced by the material
B) The stress aligned with the applied force
C) The maximum normal stress experienced by the material
D) The shear stress at the material's failure point
E) The stress perpendicular to the applied force
Answer: C) The maximum normal stress experienced by the material

58. In the context of principal stresses, what does minor principal stress refer to?
A) The shear stress experienced by a material
B) The largest stress acting on a material
C) The smallest normal stress experienced by the material
D) The stress in the direction of applied force
E) The stress experienced by a material in torsion
Answer: C) The smallest normal stress experienced by the material

59. Which of the following statements is true regarding principal stresses?
A) Principal stresses are always equal
B) Principal stresses only occur in brittle materials
C) Principal stresses are oriented at 45-degree angles to each other
D) Principal stresses do not include shear stresses
E) Principal stresses are dependent on the direction of external forces
Answer: D) Principal stresses do not include shear stresses

60. How major and minor principal stresses are typically found in a material?
A) Through direct measurement only
B) By calculating the average stress
C) Using Mohr's circle analysis
D) Solely by numerical simulation methods
E) Through visual inspection
Answer: C) Using Mohr's circle analysis

61. The principal stresses at a point in a material under stress are determined under
which condition?
A) When the shear stress is maximum
B) Where the shear stress is zero
C) When the normal stress reaches the material’s yield strength
D) Where the normal stress is zero
E) When the applied stress is uniaxial
Answer: B) Where the shear stress is zero

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62. In soil mechanics, what does the major principal stress (σ1) signify in a triaxial
compression test?
A) The vertical stress applied to compact the soil
B) The horizontal stress applied to contain the soil specimen
C) The shear stress at failure
D) The pore water pressure
E) The atmospheric pressure
Answer: A) The vertical stress applied to compact the soil

63. The minor principal stress (σ3) in soil mechanics typically represents what?
A) The maximum shear stress
B) The confining pressure in a triaxial test
C) The water table level
D) The stress due to soil weight
E) The axial load
Answer: B) The confining pressure in a triaxial test

64. When considering earth pressure against retaining structures, the major principal
stress is:
A) Always horizontal
B) Always vertical
C) Dependent on the angle of internal friction
D) Equal to the minor principal stress
E) Always at a 45-degree angle to the horizontal
Answer: A) Always horizontal

65. The concept of effective stress is crucial in soil mechanics. It primarily affects which
of the following?
A) Major Principal stress
B) Minor principal stress
C) Both major and minor principal stresses
D) Only the shear strength of soils
E) Only the compressibility of soils
Answer: C) Both major and minor principal stresses


66. The normal stress on the principal plane is known as the:
A) Shear stress
B) Radial stress
C) Principal stress
D) Circumferential stress
E) Axial stress

Answer: C) Principal stress

67. The principal planes are determined by:
A) Performing a simple tensile test
B) Using Mohr's circle analysis
C) Measuring the density of the material
D) Applying a constant temperature field

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E) Observing the material under a microscope
Answer: B) Using Mohr's circle analysis

68. When are stresses on principal planes considered to be principal stresses?
A) When they cause the material to yield
B) When they are aligned with the direction of gravity
C) When they are maximum and minimum normal stresses with zero shear stress
D) When they exceed the material’s ultimate strength
E) When they are purely shear stresses
Answer: C) When they are maximum and minimum normal stresses with zero shear stress

69. The major principal plane is characterized by which of the following?
A) Maximum shear stress
B) Minimum normal stress
C) Maximum normal stress
D) Zero shear stress
E) Constant volume strain
Answer: D) Zero shear stress

70. Principal planes are oriented at what angle relative to each other in two-dimensional
stress analysis?
A) 45 degrees
B) 90 degrees
C) 180 degrees
D) 0 degrees (they are parallel)
E) It varies depending on the material
Answer: B) 90 degrees

71. The Mohr-Coulomb failure criterion in soil mechanics, the failure occurs when:
A) The shear stress on any plane exceed the shear strength of soil.
B) The difference between major and minor principal stresses reaches a minimum value
C) The soil moisture content reaches a specific level
D) Pore water pressure becomes zero
E) The principal stresses become equal
Answer: A) The shear stress on any plane exceed the shear strength of soil.

72. On the minor principal plane, the normal stress is:
A) At its maximum value
B) Equal to the shear stress
C) At its minimum value
D) Always zero
E) Indeterminate without further information
Answer: C) At its minimum value

73. What is a failure plane in the context of materials science?
A) A plane where the material's colour changes due to stress
B) The plane along which the material has the highest resistance to failure
C) The plane along which a material is most likely to break or deform under stress
D) The plane with the maximum shear stress
E) A hypothetical plane where no stresses occur

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Answer: C) The plane along which a material is most likely to break or deform under stress

74. In geotechnical engineering, the failure plane in a soil mass is most closely associated
with:
A) The water table level
B) The orientation of bedding planes
C) The angle of internal friction
D) The colour of the soil
E) The organic content of the soil

Answer: C) The angle of internal friction

75. The Mohr-Coulomb failure criterion is used to predict the failure plane based on:
A) The maximum and minimum principal stresses
B) The electrical resistivity of the material
C) The thermal expansion coefficients
D) The acoustic properties of the material
E) The material's reflectivity
Answer: A) The maximum and minimum principal stresses

76. In the context of soil mechanics, the failure plane typically forms at an angle to the
maximum principal stress direction known as the:
A) Angle of repose
B) Angle of internal friction
C) Angle of elasticity
D) Angle of shear resistance
E) Critical resolution angle
Answer: B) Angle of internal friction

77. What does the drained angle of friction in soil mechanics represent?
A) The cohesion between soil particles
B) The maximum slope angle at which soil remains stable without support
C) The ratio of vertical to horizontal stress in soil
D) The angle that quantifies the shear strength of soil due to particle interlocking and friction
E) The water content at which soil transitions from liquid to solid state
Answer: D) The angle that quantifies the shear strength of soil due to particle interlocking
and friction

78. Which test is commonly used to determine the drained angle of friction for a soil
sample?
A) Standard penetration test (SPT)
B) Triaxial compression test under drained conditions
C) Proctor compaction test
D) Atterberg limits test
E) Permeability test
Answer: B) Triaxial compression test under drained conditions

79. How does the presence of water affect the measured value of the drained angle of
friction in soils?
A) Increases it due to lubrication

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B) Decreases it because water adds cohesion
C) Has no effect as the test is drained
D) Increases it by adding buoyancy
E) Decreases it due to pore water pressure reducing effective stress
Answer: C) Has no effect as the test is drained

80. Which soil type typically exhibits the highest drained angle of friction?
A) Silty clay
B) Peat
C) Loose sand
D) Dense gravel
E) Organic clay
Answer: D) Dense gravel

81. An increase in the drained angle of friction in sandy soils can be achieved through:
A) Saturation with water
B) Adding organic matter
C) Compaction
D) Increasing the soil's temperature
E) Reducing the effective stress
Answer: C) Compaction

82. What does the Mohr-Coulomb failure envelope represent?
A) The relationship between pore water pressure and shear strength
B) The maximum electrical conductivity of soil before failure
C) The relationship between shear stress and normal stress at failure
D) The temperature gradient necessary for soil to fail
E) The colour change in materials under stress
Answer: C) The relationship between shear stress and normal stress at failure

83. Which parameters define the Mohr-Coulomb failure envelope for a soil?
A) Permeability and porosity
B) Cohesion (c) and angle of internal friction (ϕ)
C) Bulk density and moisture content
D) Atterberg limits
E) Specific gravity and void ratio
Answer: B) Cohesion (c) and angle of internal friction (ϕ)

84. In the Mohr-Coulomb failure criterion, the angle of internal friction (ϕ) affects the
failure envelope's:
A) Slope
B) Y-intercept
C) Curvature
D) Horizontal shift
E) Vertical shift
Answer: A) Slope

85. The Mohr-Coulomb failure criterion is particularly useful for predicting the failure
of materials under which type of stress conditions?
A) Uniaxial compression only

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B) Pure torsion only
C) High-temperature conditions
D) Combined normal and shear stresses
E) Electromagnetic stresses
Answer: D) Combined normal and shear stresses

86. For a soil sample with no cohesion (c =0), the Mohr-Coulomb failure envelope passes
through the origin. This indicates that the soil:
A) Is fully saturated with water
B) Has high organic content
C) Will fail under any magnitude of stress
D) Has its shear strength only dependent on the angle of internal friction is unaffected by
normal stresses.

Answer: D) Has its shear strength only dependent on the angle of internal friction

87. For clay soil, The intersection point of the Mohr-Coulomb failure envelope with the
shear stress axis represents the:
A) Maximum possible shear stress the material can withstand
B) Soil's permeability
C) Material's porosity
D) Angle of repose of the material
E) Material's thermal conductivity
Answer: A) Maximum possible shear stress the material can withstand

88. What are the primary shear strength parameters of soil?
A) Density and viscosity
B) Cohesion and angle of internal friction
C) Permeability and porosity
D) Organic content and water content
E) Colour and texture

Answer: B) Cohesion and angle of internal friction

89. Cohesion in soils is primarily attributed to:
A) The soil’s ability to conduct heat
B) The electrostatic attraction between soil particles
C) The water content in the soil
D) The gravitational attraction between soil particles
E) The intermolecular forces present in clay particles
Answer: E) The intermolecular forces present in clay particles

90. The angle of internal friction in soil indicates:
A) The soil’s thermal conductivity
B) The electrical resistance of the soil
C) The soil's resistance to shear deformation under dry conditions
D) The magnetic properties of soil
E) The visual appearance of the soil under stress
Answer: C) The soil's resistance to shear deformation under dry conditions

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91. In the context of shear strength, sandy soils typically exhibit:
A) High cohesion and low angle of internal friction
B) Low cohesion and high angle of internal friction
C) High cohesion and high angle of internal friction
D) Low cohesion and low angle of internal friction
E) Uniform cohesion irrespective of the angle of internal friction
Answer: B) Low cohesion and high angle of internal friction

92. The Direct Shear Test is used to determine:
A) The soil’s colour and texture
B) The soil’s permeability
C) Cohesion and angle of internal friction in soil
D) The soil’s organic content
E) The soil's water retention capacity
Answer: C) Cohesion and angle of internal friction in soil

93. The Triaxial Test provides information on soil shear strength by assessing:
A) The visual aesthetics of the soil
B) The electrical properties of the soil
C) Cohesion, angle of internal friction, and the confining pressure's effect
D) The soil’s magnetic resonance
E) The soil's thermal expansion
Answer: C) Cohesion, angle of internal friction, and the confining pressure's effect

94. The concept of critical state soil mechanics is important because it:
A) Determines the soil's colour under various lighting conditions
B) Assesses the soil's ability to retain water for agricultural use
C) Predicts the soil behaviour at the point of shear failure
D) Evaluates the soil's electrical conductivity
E) Measures the soil's thermal insulation properties
Answer: C) Predicts the soil behaviour at the point of shear failure

95. In soils, the term "effective stress" is crucial because it:
A) Describes the stress responsible for the soil's shear strength
B) Measures the soil's aesthetic appeal
C) Assesses the soil's ability to conduct electricity
D) Evaluates the soil's thermal properties
E) Determines the soil's permeability
Answer: A) Describes the stress responsible for the soil's shear strength

96. An increase in the moisture content of a cohesive soil typically leads to:
A) An increase in cohesion
B) A decrease in the angle of internal friction
C) An increase in the angle of internal friction
D) A decrease in cohesion
E) No change in shear strength parameters
Answer: D) A decrease in cohesion

97. What is the primary purpose of the Direct Shear Test in soil mechanics?

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A) To determine the soil's water content
B) To measure the soil's permeability
C) To calculate the soil's compressibility
D) To assess the soil's shear strength parameters
E) To evaluate the soil's thermal conductivity
Answer: D) To assess the soil's shear strength parameters

98. Which shear strength parameters can be directly obtained from a Direct Shear
Test?
A) Cohesion and bulk density
B) Porosity and permeability
C) Cohesion and angle of internal friction
D) Thermal conductivity and specific heat
E) Organic content and plasticity index
Answer: C) Cohesion and angle of internal friction

99. During a Direct Shear Test, what is the condition of the stress state at failure?
A) Only normal stress is applied
B) Only shear stress is applied
C) Both normal and shear stresses are applied
D) Stress is completely absent
E) Only hydrostatic pressure is applied
Answer: C) Both normal and shear stresses are applied

100. What is a limitation of the Direct Shear Test?
A) It cannot be conducted in a laboratory setting
B) It can only determine the soil's water content
C) It applies a non-uniform shear stress distribution across the failure surface
D) It only measures the thermal properties of soil
E) It determines the soil's electrical conductivity
Answer: C) It applies a non-uniform shear stress distribution across the failure surface

101. In the Direct Shear Test apparatus, the soil sample is:
A) Fully saturated with water before testing
B) Placed in a confined, cylindrical container
C) Subjected to a vertical load and shear force
D) Heated to a specific temperature
E) Vibrated to simulate earthquake conditions
Answer: C) Subjected to a vertical load and shear force

102. How is shear stress induced in the soil sample during a Direct Shear Test?
A) By applying a magnetic field
B) By increasing the soil's moisture content
C) By applying a horizontal force to the top half of the sample
D) By cooling the soil sample
E) By applying an electrical current
Answer: C) By applying a horizontal force to the top half of the sample

103. The failure plane in a Direct Shear Test is:
A) Predetermined by the tester

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B) A result of the soil's natural stratification
C) Identified after the test by analysing soil particles
D) The interface between the top and bottom halves of the shear box
E) Determined by the soil's moisture content
Answer: D) The interface between the top and bottom halves of the shear box

104. Which factor does not influence the results of a Direct Shear Test?
A) Type of soil
B) Rate of shear
C) Temperature of the testing environment
D) Size of the soil particles
E) Colour of the soil
Answer: E) Colour of the soil

105. The normal stress applied during a Direct Shear Test is important because it:
A) Determines the soil's thermal expansion
B) Influences the shear strength parameters of the soil
C) Measures the soil's electrical resistance
D) Indicates the soil's permeability
E) Assesses the soil's colour stability under pressure
Answer: B) Influences the shear strength parameters of the soil

106. Why is the Direct Shear Test favoured in certain applications over the Triaxial
Compression Test?
A) It requires a larger sample size
B) It is less time-consuming and simpler to perform
C) It provides more accurate results for all types of soils
D) It can test the soil's electrical properties
E) It measures the soil's permeability
Answer: B) It is less time-consuming and simpler to perform

107. What aspect of soil behaviour does the Direct Shear Test primarily evaluate?
A) Hydration characteristics
B) Shear strength under direct loading conditions
C) Compressibility and consolidation behaviour
D) Elastic modulus and Poisson's ratio
E) Capillarity and moisture movement
Answer: B) Shear strength under direct loading conditions

108. Why the rate of shear application is considered important in a Direct Shear Test?
A) It affects the soil's thermal conductivity
B) Faster rates can lead to artificially high strength measurements due to pore water pressure
build-up in undrained conditions
C) It influences the electromagnetic properties of the soil
D) It changes the soil's colour and texture
E) Slower rates enhance the soil's permeability
Answer: B) Faster rates can lead to artificially high strength measurements due to pore water
pressure build-up in undrained conditions

109. In preparation for a Direct Shear Test, the soil sample is typically:

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A) Frozen to simulate winter conditions
B) Compacted to a specified density and moisture content
C) Saturated with a chemical solution to test chemical resistance
D) Dried in an oven to remove all moisture
E) Electrified to measure resistance
Answer: B) Compacted to a specified density and moisture content

110. The shear box used in a Direct Shear Test is designed to:
A) Apply vertical stress uniformly across the soil sample
B) Induce shear stress by rotating the soil sample
C) Allow horizontal displacement along a predefined plane
D) Measure the electrical conductivity of the soil
E) Simulate seismic activity by shaking the soil sample
Answer: C) Allow horizontal displacement along a predefined plane

111. Which of the following is not a direct outcome of the Direct Shear Test?
A) Determination of the soil's angle of internal friction
B) Calculation of the soil's cohesion
C) Measurement of soil permeability
D) Assessment of the soil's shear strength
E) All of the above
Answer: C) Measurement of soil permeability

112. The failure criterion determined by the Direct Shear Test is most closely
associated with:
A) Mohr-Coulomb failure theory
B) Hooke's law for elasticity
C) Darcy's law for fluid flow
D) Fourier's law of heat conduction
E) Newton's law of motion
Answer: A) Mohr-Coulomb failure theory

113. What is the significance of the normal load applied in the Direct Shear Test?
A) It simulates the self-weight of the soil
B) It represents the electromagnetic forces acting on the soil
C) It mimics the thermal stresses in the soil
D) It simulates the overburden pressure acting on the soil layer
E) It measures the soil's ability to absorb water
Answer: D) It simulates the overburden pressure acting on the soil layer

114. How does soil type affect the results of a Direct Shear Test?
A) Clays will show higher cohesion than sands
B) Sands will show higher cohesion than clays
C) Organic soils will exhibit the highest angle of internal friction
D) All soil types have the same shear strength characteristics
E) Soil type has no impact on the test results
Answer: A) Clays will show higher cohesion than sands

115. What limitation does the Direct Shear Test have compared to the Triaxial Test?
A) It cannot measure the soil's moisture content

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B) It provides less control over drainage conditions
C) It cannot apply varied confining pressures
D) It is unable to test soil samples at different temperatures
E) It allows for the measurement of consolidation
Answer: C) It cannot apply varied confining pressures

116. The horizontal shear force in a Direct Shear Test is applied until:
A) The soil sample completely consolidates
B) The maximum shear strength of the soil is reached, and the sample fails
C) The soil sample dries out completely
D) The soil's electrical resistance stabilizes
E) The soil sample reaches a predetermined temperature
Answer: B) The maximum shear strength of the soil is reached, and the sample fails

117. What is the main purpose of conducting a Triaxial Shear Test on soil?
A) To determine the soil's moisture content
B) To measure the soil's permeability
C) To evaluate the soil's shear strength under controlled stress conditions
D) To assess the soil's compaction level
E) To understand the soil's thermal properties
Answer: C) To evaluate the soil's shear strength under controlled stress conditions

118. Which of the following parameters can be determined from the results of a
Triaxial Shear Test?
A) The soil's colour and texture
B) Cohesion and angle of internal friction
C) The soil's magnetic properties
D) The soil's electrical conductivity
E) The soil's thermal expansion coefficient
Answer: B) Cohesion and angle of internal friction

119. In a Triaxial Shear Test, the soil sample is subjected to:
A) A single axial loads
B) Varying temperatures to test thermal degradation
C) A confining pressure and an axial stress
D) Electromagnetic forces
E) Continuous vibration to simulate seismic activity
Answer: C) A confining pressure and an axial stress

120. What distinguishes a Consolidated Undrained (CU) Triaxial Test from an
Unconsolidated Undrained (UU) Triaxial Test?
A) The CU test measures the soil's thermal properties, while the UU test does not.
B) The CU test involves consolidation under applied confining pressure before shearing,
while the UU test does not.
C) The CU test applies electromagnetic fields, while the UU test focuses on mechanical
stresses.
D) The CU test is for sandy soils only, while the UU test is for clayey soils.
E) The CU test evaluates the soil’s permeability, while the UU test measures shear strength.

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Answer: B) The CU test involves consolidation under applied confining pressure before
shearing, while the UU test does not.

121. Which of the following is a key advantage of the Triaxial Shear Test over the
Direct Shear Test?
A) It can measure the soil's colour intensity under pressure.
B) It provides a uniform stress distribution across the failure plane.
C) It evaluates the soil's ability to conduct electricity.
D) It requires smaller soil samples for testing.
E) It can determine the soil's moisture content more accurately.
Answer: B) It provides a uniform stress distribution across the failure plane.

122. The pore water pressure developed during a Triaxial Shear Test is of significant
interest because it:
A) Indicates the soil’s ability to conduct heat
B) Affects the effective stress acting on the soil particles
C) Measures the soil’s electrical conductivity
D) Determines the soil's colour change under stress
E) Reflects the soil's magnetic properties
Answer: B) Affects the effective stress acting on the soil particles

123. How does the application of confining pressure in a Triaxial Shear Test influence
soil behaviour?
A) It decreases the soil's shear strength by reducing particle interlock.
B) It has no effect on the soil's shear strength.
C) It increases the soil's shear strength by improving particle interlock and reducing pore
spaces.
D) It enhances the soil's thermal expansion properties.
E) It improves the soil's electrical conductivity.
Answer: C) It increases the soil's shear strength by improving particle interlock and reducing
pore spaces.

124. The failure criterion used in the analysis of Triaxial Shear Test data is most
commonly associated with:
A) Fourier's law of heat conduction
B) Ohm's law for electrical resistance
C) The Mohr-Coulomb failure theory
D) Hooke's law for elasticity
E) Newton's third law of motion
Answer: C) The Mohr-Coulomb failure theory

125. During a Triaxial Shear Test, the axial stress applied to the soil sample is
increased until:
A) The soil dries completely
B) The soil reaches its peak shear strength, and failure occurs
C) The electrical resistance of the soil stabilizes
D) The soil achieves a predetermined moisture content
E) The thermal properties of the soil begin to change
Answer: B) The soil reaches its peak shear strength, and failure occurs

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126. Which type of Triaxial Shear Test allows for the measurement of the soil's
volume change during shearing?
A) Unconsolidated Undrained (UU) test
B) Consolidated Undrained (CU) test with pore water pressure measurements
C) Consolidated Drained (CD) test
D) Isotropic consolidation test
E) Anisotropic consolidation test
Answer: C) Consolidated Drained (CD) test

127. What role does the cell fluid play in a Triaxial Shear Test?
A) It acts as a lubricant to reduce friction between the soil particles.
B) It simulates the effect of groundwater on soil behaviour under stress.
C) It provides a medium for electrical conductivity testing.
D) It enhances the soil’s thermal resistance during the test.
E) It colours the soil for better visualization of failure planes.
Answer: B) It simulates the effect of groundwater on soil behaviour under stress.

128. Why are strain rates controlled during a Triaxial Shear Test?
A) To ensure uniform colour development in the soil sample.
B) To prevent thermal expansion from affecting test results.
C) To minimize the impact of pore water pressure development in undrained tests.
D) To enhance the magnetic properties of the soil for measurement.
E) To simulate seasonal changes in the soil's environment.
Answer: C) To minimize the impact of pore water pressure development in undrained tests.

129. What is the significance of applying axial stress in the Triaxial Shear Test?
A) It determines the soil’s electrical resistance under stress.
B) It simulates the effect of vertical loads on soil shear strength.
C) It measures the soil’s ability to absorb water.
D) It evaluates the soil's thermal degradation under pressure.
E) It assesses the impact of stress on soil coloration.
Answer: B) It simulates the effect of vertical loads on soil shear strength.

130. In a Triaxial Shear Test, the term "effective stress" refers to:
A) The difference between total stress and pore water pressure.
B) The stress required to change the soil's colour under pressure.
C) The axial stress required to initiate thermal expansion.
D) The stress level at which the soil becomes electrically conductive.
E) The minimum stress required to alter the soil’s magnetic properties.
Answer: A) The difference between total stress and pore water pressure.

131. How does the consolidation stage affect the outcome of a Triaxial Shear Test?
A) It primarily alters the soil's colour for better test visualization.
B) It decreases the soil's electrical conductivity, affecting the shear strength measurement.
C) It allows excess pore water pressure to dissipate, stabilizing the soil structure.
D) It increases the soil’s thermal resistance by compacting the soil particles.
E) It improves the soil's magnetic properties for enhanced stress analysis.
Answer: C) It allows excess pore water pressure to dissipate, stabilizing the soil structure.

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132. Which test condition is most appropriate for evaluating the long-term stability of
slopes in clayey soils?
A) Unconsolidated Undrained (UU)
B) Consolidated Undrained (CU) with pore water measurements
C) Consolidated Drained (CD)
D) Rapid undrained test without pore water pressure measurement
E) High-temperature triaxial test
Answer: C) Consolidated Drained (CD)

133. The application of confining pressure in a Triaxial Shear Test aims to simulate:
A) The soil's natural environment under deep earth layers.
B) The effect of sunlight on soil mechanical properties.
C) The influence of wind speed on soil erosion.
D) The soil's thermal insulation properties at different depths.
E) The electrical insulation characteristics of the soil.
Answer: A) The soil's natural environment under deep earth layers.

134. During a Triaxial Shear Test, the measurement of pore water pressure is crucial
for:
A) Calculating the soil's heat capacity.
B) Understanding the soil's hydraulic conductivity.
C) Determining the effective stress acting on soil particles.
D) Evaluating the soil's resistance to electrical flow.
E) Assessing the impact of UV radiation on soil stability.
Answer: C) Determining the effective stress acting on soil particles.

135. The failure pattern observed in a Triaxial Shear Test provides insights into:
A) The soil's preferred colour under compressive stress.
B) The potential deformation mechanisms in the soil structure.
C) The soil's electromagnetic field variations under stress.
D) Changes in the soil's thermal conductivity with pressure.
E) The alteration of the soil's chemical composition under load.
Answer: B) The potential deformation mechanisms in the soil structure.

136. What information does the stress-strain curve obtained from a Triaxial Shear
Test offer?
A) The soil's elasticity and plasticity characteristics under applied stress.
B) The temperature at which the soil melts under pressure.
C) The electrical conductivity of the soil at various stress levels.
D) The change in soil colour due to stress application.
E) The soil's magnetic susceptibility under axial loads.
Answer: A) The soil's elasticity and plasticity characteristics under applied stress.

137. What does the failure envelope in the Mohr-Coulomb failure criterion represent?
A) The relationship between soil density and moisture content.
B) The boundary condition under which soil transitions from elastic to plastic behaviour.
C) The maximum shear stress that a soil can resist as a function of normal stress.
D) The linear regression line of pore water pressure against soil depth.
E) The change in soil volume under variable confining pressures.
Correct Answer: C

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142. Why is the effective stress principle important for understanding soil behaviour
under load?
A) It helps predict the settlement of foundations under future loads.
B) It is used to determine the electrical conductivity of soil.
C) It indicates the maximum load a soil can carry before becoming fully saturated.
D) It determines the change in soil volume when frozen.
E) It separates the stress carried by the soil skeleton from that carried by the pore
water.
Correct Answer: E

143. In the context of the direct shear test, why is the normal stress applied to the soil
specimen important?
A) It simulates the effect of gravity on the soil's shear strength.
B) It determines the soil's resistance to frost heave.
C) It impacts the soil's hydraulic conductivity.
D) It influences the cohesion between soil particles.
E) It affects the measured shear strength by changing the stress state of the soil.
Correct Answer: E

144. What role does the angle of internal friction (ϕ) play in the design of slopes and
retaining structures?
A) It determines the electrical resistivity of the soil used in the structure.
B) It influences the design by providing a measure of the soil's shear resistance.
C) It calculates the maximum moisture content the soil can have before failure.
D) It measures the soil's thermal conductivity for energy efficiency considerations.
E) It predicts the soil's compaction level under a specific load.
Correct Answer: B

145. Which of the following best describes the principle behind strain-controlled direct
shear tests?
A) Applying a constant rate of vertical pressure until soil failure.
B) Maintaining a constant moisture content throughout the test.
C) Applying a constant rate of shear displacement to the soil specimen.
D) Controlling the temperature within the testing environment.
E) Keeping the soil specimen at a constant density during testing.
Correct Answer: C

146. How does pore water pressure influence the effective stress in a soil sample?
A) It increases the effective stress by adding to the soil's weight.
B) It decreases the effective stress by counteracting the soil skeleton's load-bearing
capacity.
C) It has no effect on effective stress as it acts equally in all directions.
D) It enhances the soil's shear strength by creating a suction effect.
E) It alters the soil's thermal properties, indirectly affecting stress.
Correct Answer: B

147. In a triaxial test, what is the significance of measuring the change in pore water
pressure during the consolidation phase?
A) It indicates the soil's permeability to water and air.
B) It helps calculate the soil's resilience to cyclic loading.

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C) It determines the soil's elastic modulus under triaxial loading conditions.
D) It provides insight into the soil's ability to dissipate excess pore pressure under load.
E) It is used to measure the soil's thermal expansion coefficient.
Correct Answer: D

148. What is the primary advantage of conducting a vane shear test in the field?
A) It allows for direct measurement of the soil's thermal properties.
B) It provides a quick and straightforward method for estimating the undrained shear
strength of cohesive soils.
C) It can determine the soil's permeability and porosity in situ.
D) It measures the electrical resistivity of the soil for grounding purposes.
E) It assesses the soil's compaction level without disturbing its natural state.
Correct Answer: B

149. Which statement best describes the principle behind the direct shear test for
determining soil shear strength?
A) The soil specimen is subjected to a triaxial pressure system to simulate real-world
stress conditions.
B) A vertical load is applied rapidly to the soil specimen until failure occurs without any
lateral support.
C) Shear force is applied directly to the soil specimen until it fails along a predetermined
plane.
D) A vane is rotated within the soil to measure the torque required to cause soil failure.
E) Soil specimen is allowed to consolidate under a vertical load before shearing is
applied.
Correct Answer: C

150. In the context of shear strength determination, the term 'principal planes' refers to:
A) The planes along which the maximum stresses act.
B) The horizontal and vertical planes within the soil mass.
C) Any plane where the shear stress is zero.
D) The planes where only normal stresses act and shear stresses are maximized.
E) The planes of symmetry in the soil's crystalline structure.
Correct Answer: C

151. The Mohr-Coulomb failure criterion linearly relates shear strength to normal
stress. What parameters define this relationship?
A) Cohesion (c) and the angle of internal friction (ϕ)
B) Bulk density and porosity of the soil
C) Soil's liquid and plastic limits
D) Compressive and tensile strengths of the soil
E) The soil's specific gravity and saturation level
Correct Answer: A

152. Which test method involves increasing axial stress while keeping the specimen
under a constant confining pressure to induce shear failure?
A) Vane shear test
B) Direct shear test
C) Unconfined compression test
D) Triaxial shear test

27. Page 27 of 32

E) Consolidation test
Correct Answer: D

153. For a saturated soil sample, the effective stress (σ′) is crucial (important) because:
A) It represents the total weight of the soil sample.
B) It indicates the soil's resistance to plastic deformation.
C) It reflects the stress transmitted through the soil's pore water.
D) It is the stress carried by the soil skeleton, excluding the effects of pore water
pressure.
E) It determines the electrical conductivity of the soil.
Correct Answer: D

154. How does the undrained shear strength (cu) of fully saturated clays typically
compare between unconsolidated-undrained triaxial tests and unconfined
compression tests?
A) cu values from unconsolidated-undrained triaxial tests are usually higher.
B) cu values are identical in both tests.
C) Unconfined compression tests yield higher cu values due to rapid loading.
D) The testing method has no significant effect on cu values.
E) cu values are unpredictable and highly variable between tests.
Correct Answer: A

155. The critical state of soil is a concept used to describe:
A) The maximum dry density achievable through compaction.
B) A condition where soil behaves neither purely elastically nor plastically.
C) The state at which the soil's shear strength is fully mobilized without any
change in volume.
D) The threshold at which soil transitions from a solid to a liquid state.
E) The optimal moisture content for soil compaction.
Correct Answer: C

156. In soil mechanics, the angle of internal friction (ϕ) is significant because it:
A) Directly correlates with the soil's permeability.
B) Determines the soil's capacity to resist sliding along failure planes.
C) Is inversely related to the soil's compressibility.
D) Indicates the maximum angle of a slope made of the soil that can remain
stable.
E) Reflects the electromagnetic properties of soil.
Correct Answer: B

157. What is the principal purpose of the Mohr-Coulomb failure criterion in soil
mechanics?
A) To estimate the soil's permeability
B) To determine the soil's maximum allowable bearing capacity
C) To describe the functional relationship between normal stress and shear stress
on a failure plane
D) To calculate the soil's consolidation rate
E) To measure the soil's resistance to erosion
Correct Answer: C

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158. In a direct shear test, how is the angle of internal friction (ϕ′) determined?
A) Through the slope of the line in a plot of shear stress versus normal stress
B) By measuring the change in height of the soil specimen
C) By applying a uniform shear force until failure occurs
D) Calculating the difference between major and minor principal stresses
E) Using the soil's cohesion value
Correct Answer: A

159. During a triaxial shear test, the term 'deviator stress' refers to:
A) The summation of the major and minor principal stresses at failure
B) The axial stress applied to the specimen to cause shear failure
C) The confining pressure applied to the specimen
D) The increase in pore water pressure during the test
E) The residual strength of the soil after testing
Correct Answer: B

160. Which factor does NOT influence the result of a vane shear test?
A) The diameter of the shear vane
B) The height of the shear vane
C) The angle of internal friction of the soil
D) The mobilization of undrained shear strength
E) The torque applied to the shear vane
Correct Answer: C

161. In the context of the Mohr-Coulomb failure criterion, what does the term 'cohesion'
(c) represent?
A) The internal angle of friction between soil particles
B) The water content of the soil
C) The atmospheric pressure on the soil
D) The inherent shear strength of soil at zero normal stress
E) The density of the soil
Correct Answer: D

162. What is the significance of the critical void ratio in soil mechanics?
A) It represents the moisture content at which soil becomes fully saturated
B) It denotes the maximum density the soil can achieve under loading
C) It is the void ratio at which the shear strength of the soil is maximum
D) It indicates the void ratio at which loose and dense sands have practically the
same shear strength
E) It is used to calculate the soil's permeability
Correct Answer: D

163. Which test is best suited for determining the undrained shear strength of fully
saturated clays?
A) Direct simple shear test
B) Unconsolidated-undrained triaxial test
C) Vane shear test
D) Direct shear test
E) Consolidated-drained triaxial test
Correct Answer: B

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164. The concept of 'effective stress' is crucial in soil mechanics because:
A) It helps in determining the soil's plastic limit
B) It indicates the soil's capacity to resist compaction
C) It represents the stress carried by the soil skeleton, excluding pore water
pressure
D) It is used to calculate the soil's liquid limit
E) It determines the soil's electrical conductivity
Correct Answer: C

165. What is the shear strength of a soil mass primarily a measure of?
A) The soil's ability to resist compaction
B) The internal resistance per unit area the soil mass can offer to resist failure and
sliding along any plane inside it
C) The soil's capacity to absorb water
D) The maximum normal stress the soil can withstand
E) The soil's resistance to erosion
Correct Answer: B

166. What does the angle of internal friction (ϕ) represent in soil mechanics?
A) The cohesion between soil particles
B) The internal angle at which failure occurs due to shear stress
C) The compaction level of the soil
D) The resistance of soil to erosion
E) The slope of the failure envelope in the Mohr-Coulomb criterion
Correct Answer: E

167. In the context of shear strength of soil, effective stress (σ′) is defined as:
A) The total normal stress minus the pore water pressure
B) The total shear stress plus the normal stress
C) The cohesion of the soil
D) The angle of internal friction
E) The total stress applied on the soil
Correct Answer: A

168. Which laboratory test is considered one of the most reliable methods for
determining shear strength parameters of soil?
A) Direct simple shear test
B) Triaxial shear test
C) Vane shear test
D) Direct shear test
E) Torsional ring shear test
Correct Answer: B

169. The vane shear test is particularly useful for estimating the undrained shear
strength of which type of soil?
A) Loose sand
B) Dense sand
C) Very soft to medium cohesive soils
D) Overconsolidated clays
E) Silt

30. Page 30 of 32

Correct Answer: C

170. The shear strength in cohesion less soil is due to:
A) Internal friction
B) Cohesion
C) Intergranular friction
D) Interparticle force
Answer: Option (C)

171. Major Principal Stress in a soil is represented by the symbol:
A) σ1
B) σ2
C) σ3
D) σ4
Answer: Option (A)

172. The maximum shear stress τmax, for a soil mass is equal to:
A) (σ1 – σ3 )/2
B) (σ1 + σ3 )/2
C) (σ1×σ3 )/2
D) (σ3 – σ1 )/2
Answer: Option (A)

173. A major difference between the direct shear test and tri axial shear test is:
A) Control on the drainage level
B) Stress condition
C) None of the mentioned
D) All of the mentioned
Answer: Option (A)

174. The Tri axial compression test was introduced by:
A) A. casagrande and Karl Terzaghi
B) Mohr
C) None of the mentioned
D) All of the mentioned
Answer: Option (A)

175. Which of the following outlet is provided at the base of the tri axial test apparatus?
A) Cell fluid inlet
B) Pore water outlet
C) Drainage outlet
D) All of the mentioned
Answer: Option (D)

176. Pore pressure developed in the tri axial test can be measured by:
A) Bishop’s apparatus
B) Pore pressure apparatus
C) Terzaghi’s apparatus
D) Mohr’s apparatus
Answer: Option (A)

31. Page 31 of 32

177. The deviator stress developed in the proving ring, through the applied pressure is
equal to are:
A) σ1 + σ3
B) σ1 – σ3
C) σ2 – σ3
D) σ2 + σ1
Answer: Option (B)

178. The deviator stress σd is given by:
A) σd = σ1 + σ
B) σd = σ3 – σ1
C) σd=additional axial load/A2
D) σd = σ2 – σ3
Answer: Option (C)

179. In unconfined compression test the value of σ3 is equal to:
A) 1
B) 0
C) 0.5
D) ½
Answer: Option (B)

180. The unconfined compression test is derived from:
A) Direct shear test
B) Vane shear test
C) Tri axial compression tests
D) Drained test
Answer: Option (C)

181. The unconfined compression test is generally applicable to:
A) Unsaturated clay
B) Saturated clay
C) Fine grained soil
D) Coarse grained soil
Answer: Option (B)

182. When the Mohr circle is drawn in a confined compression test, its radius will be
equal to:
A) Cu
B) qu
C) Ru
D) None of the mentioned
Answer: Option (A)

183. What will be the shearing resistance (undrained shear strength) of a sample of clay
in an unconfined compression test, falls under a load of 150 N? Take change of
cross-section Af=2181.7 mm2.
A) 68.75 kN/m2
B) 34.38 kN/m2
C) 11.35 kN/m2

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D) 0.6875 kN/m2
Answer: Option (B)

184. The unconfined compression test is derived from:
A) Direct shear test
B) Vane shear test
C) Tri axial compression tests
D) Drained test
Answer: Option (B)
185. What is the main disadvantage of the shear box test?
A) It can only measure the shear strength of cohesive soils
B) The shear area changes during the test, causing an unequal distribution of shear
stress
C) It allows for the measurement of pore water pressure
D) The test is too quick to provide accurate results
E) It cannot be used for determining the angle of internal friction
Correct Answer: B